The best tip is a cliche: you have to communicate with him. The way someone likes to be sucked is very particular and you can moan when he does something nice, say ‘slowly’, ‘softer’ and things like that to guide and help him. Don’t be shy and help him, you deserve this pleasure.
And… make him read this, and then practise!
https://female-orgasm-denial.tumblr.com/post/157590444398/how-to-give-cunnilingus-like-a-superstar