And it usually starts out normal, but sometimes one person might lick at the other's lips- or someone opens theirs as an invitation! After that, well, you kind of use your tongue to like...

Explore the other person's mouth? Shut up! I know it sounds weird!
[She starts nervously scratching her head. Darn it, she sounds like a weirdo idiot trying to explain this! Maybe she should just demonstrate? Ugh!]