i really liked it when my bf would suck my clit. he did a combination of licks and sucks that threw me over the edge! one thing i don't like personally, is the insertion of a finger when i'm not quite ready for it. it feels harsh to have a finger pushed in when its not quite wet enough nor ready for any insertion for that matter. but once i'm wet enough, the stimulation of the upper vaginal wall with a finger during cunninglingus always gives me an orgasm.

pay attention to her breathing patterns. usually the faster short breaths indicate she's getting close. also the tensness of her legs. my leg muscles would always tighten up, and my bf would have to be careful when that happens, cuz i snapped his head between my thighs as a reflex, i couldn't control it, honestly! heehee

good luck!