My question is one that has been posed to me on many occations by many a frustrated teenager. They hear all the information about sex and everything that goes with it, but the one question which I still find being asked all the time is... "How far is too far?" as well as ways to prevent themselves from reaching these boundaries. Would it be possible for an article to be written from a biblical perspective on how far is too far and ways to prevent adolescents from crossing these boundries?
Since I have worked with high school students and addressed this issue a lot, let me share what wisdom I have gleaned from others and learned from the Word.
Another way to phrase your question is, "Where should I draw the line?"
The line is the place where our behavior moves from that which glorifies God, to that which is sin or leads to sin (either mental or physical sin).
Scripture says, "It is good for a man not to touch a woman" (1 Cor. 7:1). One of the meanings for the Greek word for "touch" means "to press against in such a way as to kindle or catch on fire." So another way to translate this verse would be, "It is good for a man not to touch a woman so that they become sexually aroused."
This is true wisdom, because once people become sexually aroused, hormones kick in and it gets hard to think rationally. So it is far easier to stay in control by limiting our behavior to that which isn't sexual.
I suggest that this means not touching anyone in a way you wouldn't dream of touching one's pastor (or pastor's wife, depending on your gender), or family member. When it comes to dating couples, that means not kissing each other with anything more than you'd give your sister or brother.
So the bottom line is, I suggest that "the line" should be drawn between a short kiss and a long kiss. Short kisses are not necessarily sexual, but long kisses are. Sexual arousal happens after you cross the line from a short kiss to a long kiss. Sexual activity outside of marriage is the sin the Bible calls fornication; it's a sin because God wants all sex (and sexual activity, even if it's far short of intercourse) to be contained within marriage since it's so powerful. Many kids define sex as intercourse, but God's view of sex is far broader than that. Even physiologically, we can tell that sexual feelings occur as a result of doing things that are a long way from intercourse.
Things become startlingly clear when you think: "What if I touch or kiss my brother or sister in this way?" If the thought of French kissing your sibling grosses you out (and I hope it would), then that means it's sexual, and it falls in the category of "off limits."
This discussion is a different approach from "How far is too far," because that question really means "How close to the edge of the cliff can I walk without falling off?" God wants us to ask, "What do I need to do to stay holy and glorify God in everything I do?"
I hope this helps.
P.S. Have you checked out the article called "Why Wait Till Marriage?"