Well, it has to be sort of private, and when things get kind of quite. Usually you know the guy is getting ready to kiss you because he is looking at you or at your lips and leans in slightly etc. Both of you are turned towards each other obviously, you can usually sense when to do this based on the situation.
I think the BEST way to kiss is Frenching, i dunno i like it, but if it's a first kiss you might want to go with something more subtle. Like a heart felt kiss, closed mouth, if things get more comfortable then well ..... ME