Communication is always key. Ask for it and provide it. It also occurs in non verbal ways. The clit is a small round “bump” just at the top of her vagina that contains an insane concentration of nerves (think about the base of your head of your dick, how sensitive that is and you get the idea). That being said, be gentle with it and don’t smack it around or jackhammer it. For some girls it’s buried deep under a “hood” for others it’s more prominent or larger. They vary as much as dicks. But watch for her non-verbal cues (moaning: good, wincing: bad) and you’ll be just fine.