Hiii. Good question honestly. My first advice—read a lot of smut. You can understand better that way what one could do during sex and what one (author) could describe. Other than that, you need to think of sex as a way to explore your characters. Both physically and psychologically. Your goal is not just try to make it hot. You need to make it human first so that it doesn't read as cheap novel moms keep in their closets hshs. Imagine your characters and go at it with understanding that you are watching from behind their shoulders but you also kinda... The one who makes them move and think? So in the end two advices—read and immerse yourself in the act hhh. Also two mini-advices—practice and don't be afraid to throw in some spice like kinks and fetishes.