One of the best things for the development of a complex personality and stable identity of a tulpa is to simply expose them to many things. Not so inccidently, this advice holds true for people other than tulpas as well- however, there are differences. Tulpas are born with decades of preconceptions: the memories of the host. Whether or not the tulpa openly accesses or identifies with the memory of the host, they will surely be influenced by these preconceptions. Most of the time, hosts eat foods they know they enjoy, play games they know they like to play, and think about things that are important to them. All tulpas will have some overlap with their hosts and this is natural, as the tulpa-host bond is even closer than identical twins. Still, a host who wishes their tulpa to develop a complex and independent identity would be wise to encourage a sort of natural divergence.
Natural divergence creates differences such as loving a food the host merely tolerates, relating to a book character more than the host did, or having a different favorite band. The little things add up over time. These natural divergences gradually cement into personality traits and preferences.
The first few days of life, a tulpa should be kept close to the heart. They are too busy getting used to the internal side of things for you to even think about trying to get them to pay attention to external things. Next, for the first few weeks or until reliable basic vocality (the ability to have a verbal interaction), these suggestions should be taken lightly. Instead, the level of structure you have with your tulpa should be kept high: engagement should be purposeful and media exposure should be intentional and pure-hearted. If you met someone who was new to your country, and you wanted to befriend them, would you want the first song you share with them to be the nastiest, trashiest song you know? For tulpas, the situation is even more serious. They have never heard any music before. Show very young tulpas the best of the best, and these purposeful experiences will become wonderful foundational memories.
The best and most simple advice is simply to mentally point things out. Speak to your tulpa like they are very curious about the world and encourage them to act curious. Even a tulpa who is pre-verbal can project a feeling that says, "What is this? This is new to me." At this cue, think back to your tulpa about your personal experiences and thoughts about it, or describe what it is. This can be a one-off interaction or the start of a longer conversation, but it should be frequent either way.
This is often called narration but it can and should be broader than narrating your own actions. The way mirrors steam up after a hot shower, the bitter aftertaste of an overly sweetened candy, and the way the wind gracefully moves tree branches are not things that you do. Yet, they are meaningful to point out to a infant tulpa who has never really noticed them before. Your words may pave the path for your tulpa to chase deeply relaxing experiences, bake high-quality sweets, or grow beautifully flowing hair.
Keep in mind that your tulpa is developing rapidly and the way they act may change from hour to hour, day to day, or week to week. If they start behaving or identifying in a bad way you strongly disagree with, the first thing you should do is gently explain your disagreement. Try not to react as if they were "naughty", but instead as if they were a foreigner who accidently used a word they do not realize is a curse word. Correct them with kindness. They may be acting out just to see what happens or how they will be treated for behaving strangely, so don't get too angry: their curiosity is a good thing. Times when they act badly can become a chance to teach your tulpa how to have morals and principles. Hosts have an immense amount of sway in how their tulpas behave, so don't worry about a tulpa "being corrupted", "going wild", or "turning evil" at random. You will always be there for them. When a tulpa interacts with the host they recieve telepathic, mental feedback. Other people only see your external reactions, like the expression on your face, but a tulpa will directly be able to see into your heart. They will learn how you want them to act quicker than anyone else ever could. This is one of the special powers of tulpas and something you should treasure and value deeply about them. You can value this by encouraging your tulpa toward healthy habits and traits. Who knows? A healthy, mature tulpa might return your heart-touching encouragement tenfold.
There is one major danger to the formerly mentioned immense sway of the host: talking with lots of people on the internet. When very young tulpas get their interactions through the internet, they do not have the benefit of mental feedback, and they probably don't even get facial expressions- just emoji. The quality of interactions on the internet varies wildly, and most parts of the tulpamancy community are hardly paltable. Even if you like talking to people on the internet, you would be wise to keep an infant tulpa away from talking online for at least several months. Most people on the internet in places like Reddit or Discord don't stay long. However, the relationship between you and your tulpa is for the rest of their life.
Your tulpa is at an important stage in life where they are developing their identity. Do you want them to develop their identity for talking on the internet? Or for being with you? They will always be able to start talking online when they are older and have a stronger, more stable identity. But you won't be able to get back their earliest childhood days if they waste them with faceless strangers instead of you.
You've been together for many months, a year, or a few years now. Vocality isn't an issue: your tulpa can hold a conversation. It usually doesn't take effort for you to rouse them in order to interact or talk. You've mostly settled into the swing of things, but you recognize your tulpa is still very young. They might not really have a solid place in your life and they might not really have long-term goals or aspirations of their own. Your tulpa -while you still love them- might start to feel.... Shallow. Uninteresting. Maybe even.... Fake. You might worry they're developing too slowly as the newness wears off. Fledgling tulpas benefit the most from a broad exposure to what the world has to offer. This is the prime time for exploration.
Tulpas do need time to develop. It won't happen without effort. You should try to have a time in the day just for you and them to be together. But even if you are busy, there are plenty of ways to provide interesting, new experiences for your tulpa to benefit from. And you never know- you too might become a more developed, well-rounded person by exposing yourself to new things.
Not all tulpas control the external body, and many more tulpas and hosts blame lack of development on a tulpa not controlling the body enough. So, all the following suggestions will not even address things that a tulpa can do when controlling the body. It is not required for a tulpa to use the body to develop a strong and healthy identity. In fact, when tulpas control the external body (often called possession or switching), it can even hinder development!
Tulpas manage to be different from the host by distancing themselves from the host's identity. You might be very shy, but your tulpa is extremely extroverted. They are able to speak to you internally and be super extroverted and develop as an extroverted person, slowly forming more internal beliefs around it and having extroversion cemented into them. However, if your tulpa controls your body, things will change. The host identity is not just in the brain: it's cemented into the body. In order to control the body at all, tulpas have to give up some of their distancing. When they identify with the body, they will most likely not be able to behave the same way. The extroverted tulpa won't be able to act the same way in public as they do internally with the host. Because the host always gets shy and nervous, the tulpa will physically experience being shy and nervous. This will keep them from developing as an extroverted person, because it's not how extroverts are- it's how shy people are. When young tulpas use the body, their identities will generally become more like the host's because they will have the physical experience of the host.
If your fledgling tulpa has a trait you both think is highly valuable, that you don't have, protect it. If you try to make them use the body all the time because you think they will be better than you at living your life, you'll most likely be wrong. Even the strongest trait in fledgling tulpa can disappear immediately when using the body. If you always think depressing thoughts, but your tulpa is mostly free of your thought patterns, it is most likely due to their distance from your external life. If you thrust them into external life and your external body, they will almost certainly begin to display simmilar depressing thought patterns. So protect the personality traits, identity, and life of your fledgling tulpa by not trying to make them live your life.
The main life of a tulpa is internally-based: perceptions, emotions, thoughts, and beliefs. Tulpas who don't percieve, feel, think, or believe, suffer developmentally. When the host makes the tulpa do these things, the result is generally unintersting, unamusing, or preditcable. It's what the host expects. So, tulpas need to learn to percieve, feel, think, and believe on their own, instead of being forced along by their hosts. These skills develop gradually and at different rates for everyone, which is why this is a phase of development that lasts years or even decades. Tulpas that do not progress and do not develop these skills, however, tend to fall by the wayside as the host's life gets busier or changes, and the host loses their dedication or interest in the tulpa.
At this point, the effort should gradually be less and less the host's, and more and more the intentional effort of the tulpa. The host should not need to point out the existence of experiences like steam on a mirror or the way trees move in the breeze for the tulpa to oftentimes have perceptions like this. When viewing media, tulpas should learn to form their own mental understandings of the plot, relate to the characters, and generally experience the media alongisde the host. They should have their own view- not just leeching off the host's perception.
This may cause a perception of a tulpa "becoming dumber." Most tulpas are mentally (and physically) capable of everything the host can do mentally (or physically.) If you have painted a thousand landscapes, your tulpa could most likely "steal your style" or "skinwalk" you and paint a landscape exactly the same way. Younger tulpas may act this way for months or even years. However, when they begin to develop "their own style", their skills as an independent identity, they may abruptly stop being able to act like you act. Instead of a sensible landscape painting, they might paint in a different way that looks bad- because they aren't skilled yet. However, most people would consider it an improvement for an artist to start developing their own style instead of simply copying the masters.
Painting style is an easy example, but not all hosts or tulpas are painters. However, remember this metaphor as your tulpa develops. Be kind to them if they suddenly aren't "as good as you." You've had all of your life to learn what you know. They have only had a fraction of your time on earth. Tulpas are people who have to learn how to be people in a body and brain that has already learned how to be somebody else. Let them exist, let them experiment safely, let them grow at their own pace and most of all, if you want a lifelong tulpa, let them have a life.
Ask your tulpa sincere questions. Most people are thrust into thinking sincere questions because of their responsibilites. Teachers and caregivers ask children from young ages, "What do you want to be when you grow up?" Have you ever asked your tulpa what they want to be in the future? Most people have to think about what sort of work they want to do because they need to work to afford their lifestyles, like paying rent for housing and buying food and clothes. Most tulpas don't work for money, but they live with a host. More than a stay-at-home parent, they are a stay-in-head friend. Foster a sense of responsibility in your tulpa towards the life you share together, and your tulpa will always have a reason to wake up in the morning and try to be a good person: You. (Hosts can and should do the same.)