A 6'5 lightskin I knew from high school used to yap with girls about stories he had experienced, like parties, nights where he and his friends messed around, fights etc. He also talked about basic philosophical, ethical and social topics. Music, gym, movies, TV shows... All that shit man... It really sounds simpler than it is. Problem is basically all incels haven't experienced shit in life so no stories to talk about it.
/edit: Mb, you meant face to face with a girl alone. I wouldn't know man. Probably like above but in a way slower pace. Also more about her, her hobbies etc... I think your goal would be to let talk her as much as possible.