Blow job help

So me my boyfriend mess around all the time and he always eats me out and I want to reciprocate that favor for him and give him a blow job. Problem being I have never done this before and I’m not really sure what to do. I know you’re supposed to keep your teeth far away but how do you do that? What exactly should I do? If I my teeth accidentally hit him gently will that ruin it? How do make it as good for him as he makes it for me? Please just give me a crash course or share some tips☺️