look for something unique you like about her, I dunno, like her smile, or dimples or something. I always get comments about my eyes so I'm just like oh thanks, but when someone comments about something not easy to notice, I take note of it. when some guy says to me "you're gorgeous" when I just meet them, my first thought is "ok, stop buttering me up because you want some tonight" so don't say "you're hot" or "you're sexy". so be truthful, don't bullsh*t
ya, the you're hot or you're sexy are actually a turn-off for me.
on the other hand, I find it random but sometimes I get: I like your hair today, or I like your makeup, cause I don't often wear makeup I guess, so it's more noticeable. the second one came from a guy I know likes me, but the first one is just random.. hopefully good? either way, I remember those more than anything else. so like truejbig said, unusual things are more memorable.
Personally, I prefer "you're cute" or "you look really nice today" or compliments about my eyes or smile over "you're hot" and "you're sexy." The last two usually just make me laugh when I hear them, whereas the other ones seem more meaningful, flattering, and sweet! But that's just my opinion :).
depends how you say it. the you're hot/cute/sexy thing can p*ss some girls off because they think you just like them for that reason. for some girls it is flattering. try to point out special things that you like about her. her eyes changes colors in the sun, you like when she smiles a certain way, you like the way her laugh sounds. it all sounds stupid, but it works most of the time, especially when you mean it
Look for context when you're complementing a girl.
If the girl is aggressive, and passionate, "sexy" would most likely not insult her. If the girl is more girl and playful, "beautiful" or "pretty". If its halloween and she's in a costume, or if she's playing with her younger cousins, "cute" is an endearing compliment.
Be aware of how the girl views herself, and aware of her feelings towards you, and use this knowledge to shape your feelings towards her into a nice word or gesture that will make her feel good about herself, and about YOU.