Plenty of people go through relationships like Kleenexes. Of course, some think a bit more carefully and realize that it's probably easier and more effective in the long run to just get a handkerchief. Yes, a handkerchief is a bit more costly, but no longer do you have to worry about where that next tissue is going to come from. The handkerchief will be there. (Still, sometimes handkerchiefs need replacing. But I'll stop here.)
Listen carefully to people who go on and on about how great their boyfriends or girlfriends are. Sometimes, the person has a truly caring, sweet boyfriend or girlfriend who loves her and works hard to make her happy. This person may genuinely be in love-- but chances are, that boyfriend or girlfriend didn't fall out of the sky.
Then there's that person who has a new date every week or two. Cynical people might say that these people are only pushing their own feelings of insecurity off on everybody else, and the only way they can feel secure is because they can get attention from boys/girls. When these people talk about love, they generally don't know what they're talking about. What does it mean to be in love after two weeks? Besides, if you date that many people, you're probably too caught up in yourself to get to know your partners.
Here's the difference: the first person thinks his or her date is great, while the second thinks dating is great.
Ideally we could always date someone really sweet who could connect with us on a deep level but still share in all the fun besides. Unfortunately, this is rarely possible. So we're given a choice-- do you date people you don't care about so much, or do you wait for someone you really like?
Before you start dating, ask yourself: "What do I want out of a relationship?" Dating "just because" that's the thing to do isn't going to make you happy. Dating because you're tired of being single will be a change of scenery, but it won't solve your loneliness problem.
You choose whether to date for serious involvement or fun, but don't confuse the two: you can't have love in a fling and going long-term won't always be light-hearted fun.
You won't (and shouldn't) know everything about your partner before you start going out, but you should know something. Getting to know each other before you get involved will tell you volumes about whether you're compatible or not, while also sparing you from jumping into a relationship that wouldn't work. Especially if you want a serious relationship, get acquainted before you start dating-- besides, how can you know you want to be serious when you don't even know $him?
In life, obviously, you'll probably be in both kinds of relationships: serious and casual. But you don't have to start in high school. You have plenty of time. In the great scheme of things, high school isn't really important. Plenty of normal, highly successful, romantically successful people never dated in high school. But boy, are there a lot of ways to screw up if you do.