It's been ages since I've dated. (Married 11 years - get off my lawn, you young whippersnappers! *waves her cane*) But what's always gotten me - for my exes as well as my husband - are:
Physical: The eyes. It's a combination of the color (blue or hazel = swoon) and the way the person looks at you - the eyes really are a window to the soul.
Personality: Combination of sense of humor and geekiness. If I had to pick one over the other, it would be sense of humor.
Fortunately, my husband has all of the requisites: sense of humor, geekiness, hazel eyes, and (as I put it) "tells" so obvious that he can't even play
online poker.