This seems to be the most popular question. Jason Evert gives an excellent answer.
A related topic is whether or not french kissing is a good idea. Again, Jason Evert provides some great food for thought, including this: "Nevertheless, some say that French kissing is really no big deal and does not mean anything. But isn’t there something in you that wants it to be a big deal? The more of ourselves we give away, the less we value the gift of our body and our entire self (and people will respond by treating us with less respect as well). Ask yourself what your kisses are worth. Are they a way to repay a guy for a nice evening? Are they a solution to boredom on a date? Are they a way to cover up hurts or loneliness? Even worse, are they merely for 'harmless' fun? If the answer to any of these questions is yes, then we have forgotten the purpose of a kiss and the meaning of intimacy. So do not segregate parts of your sexuality as 'no big deal.' Your entire body is an infinitely big deal, and this includes your kisses. If we realize this, the simplest of kisses becomes priceless and brings more joy than one hundred one-night stands."