What does it mean to call yourself a Buddhist? Are there specific things you have to do or believe, or is it up to you?
Of course, anybody is free to draw on Buddhist principles and techniques they find helpful and to think of themselves as a Buddhist if they want. But it’s not a total free-for-all. Buddhists have lots of differing beliefs and practices, but there are a few shared principles that define them as Buddhists. These are the fundamental discoveries the Buddha made, and if you accept their truth, you’re a Buddhist.
Thich Nhat Hanh describes them this way: impermanence (everything is always changing), no self (nothing has a solid core or soul), and nirvana (peace is freedom from fixed concepts). In his great book What Makes You Not a Buddhist, Dzongsar Khyentse describes them as: All compounded things are impermanent, all emotions are pain, all things have no inherent existence, and nirvana is beyond concepts.
If you accept these principles, you can then make a formal commitment to Buddhism in a ceremony called “taking refuge.” Because nirvana means giving up ego’s futile search for refuge from impermanence and no self, the twist is that you’re taking refuge in not seeking a refuge. If you can do that, you’re really a Buddhist.