Talk with your partner. Only do what both of you are comfortable with and actually want to do. Have a conversation - multiple conversations! - about sex, your boundaries, and what you want to try. (Do this well beforehand: not while you're ripping each others' clothes off.) If you don't know what your boundaries are, then think about them! Make three lists: what you want to try (or what you're comfortable with), what you may want to try (or what you're not sure about), and what you absolutely don't want to try (not negotiable). And masturbate! It helps you learn what you like (and it feels good). That way, you can tell your partner what you like and don't like. You have to be comfortable talking about it with them and giving them instructions. If you're not comfortable talking about it, then you're probably not ready to do it. Be comfortable with saying "No," or "Not yet," or "I'm not sure, maybe we should wait," or "Slow down," or "Yes, but go slowly," or "Do this, but not that," or "Yes, do that again!" Practice saying it aloud by yourself if you need to. And respect your partner when they say these things, or something like them. Don't pressure them, or try to persuade them, to do something they don't want to do. Let them know it's okay if they're not ready, and keep the lines of communication open. Communication is the most important part - communication and respect!