First kisses are always something special. Of course, because people understand this, they often work very hard to perfect that first kiss, planning out every last detail. Ultimately, however, they are disappointed. Why?
The details do not make the kiss special; the wonder is what happens, not the specifics. The spontaneity-- the unplanned "I kiss you because I want to; you kiss me because you want to" is where the magic lies.
First kisses are great because you're kissing a guy or girl you like who likes you, not because they're "great" kisses. Most are awkward-- which makes sense; it is your first, after all! What doesn't make sense is planning everything out, because then you'll expect something that's not, which will certainly disappoint.
Kissing is an art. You can't plan art.
A first kiss is a special step into the world of romance, not the ultimate kiss. Why should it be? If it was, what would you look forward to?
Think short, soft, and sweet. Don't trouble yourself with anything heavy like tongue. Keep it simple. There's plenty of time for other stuff later.
Most first kiss horror stories are from people who tried too hard and rushed with the wrong person. Lighten up. Relax. If you trust and like the guy or girl you're with, there's nothing to worry about. Even if things aren't quite right the first time, you'll have myriad opportunities later.
When should you kiss? Some couples kiss on the first date; others take a few months. Do what you feel comfortable with. If you're ready, go for it, but if not, waiting serves a purpose too.
Side note: there's no rule that says guys or girls have to make the first move. It is perfectly acceptable for to initiate the kiss, provided your partner doesn't say anything like, "Well, I hope you don't kiss me until I'm ready."
Do you need to ask? Some people think it ruins the romance, but others insist you question first. Usually, however, you can tell if someone is interested. If the person is very shy or jumpy, you don't want to scare him or her, and in that case you probably should ask, but generally, it's probably unnecessary.
Kissing is an art, not a science, and there is no hard-and-fast rule for when the time is right. Just use your brain: you're sitting on a bench with your boyfriend (or girlfriend) alone together; he/she moves closer; he/she puts his arm around you; you're staring into each other's eyes, talking softly; his/her face moves closer to yours; he/she glances down at your lips-- is there anybody who can't tell this person wants to kiss?
Yes, it isn't always that obvious, but you should be able to get a feel for it, even with limited experience. If, however, you really are confused, don't be afraid to ask! Asking is unnecessary only if you can tell. If you can't, it's no big deal: just ask!
Remember, just don't plan too much: choose the right person, but after that, there's no need to worry about the specifics. The who is far more important than the what.