Online dating CAN be great, but there are plenty of pitfalls as well. The big pluses for OD are that you get much greater exposure to many more people than you probably get in your normal life, AND that you can filter out people who aren't a good match (assuming they did a good job building their profile), saving both of you wasted time and effort.
Know that if you're a good-looking girl, you're going to get a ton of guys who are "window-lickers"; guys who are trying to hit on you just based on your looks. Many will be directly sexual with their offers. Every decent-looking girl deals with that, and you have to have a thick-enough skin to just delete those emails and move on. Don't bother replying; you'd just be wasting your time.
Concentrate on the guys who write to you and actually have something to say, and know how to say it. Guys who treat you like a person instead of a call girl or stripper. If they can't compose a few sentences properly and introduce themselves, you probably wouldn't get much out of a date with them either, no matter how good that picture of them might look.
Finally, you aren't going to meet a ton of guys online who look like they could be on TV. Most really good-looking guys get enough interest in the real world that they aren't online; they're either taken or busy juggling 3 girls. You'll have a few guys above average, but most are going to be average or below. Looks aren't everything, but again, keep your expectations reasonable.
If you meet someone you like, email them back and forth a few times and ask plenty of questions. If things are going good, try to set up a video chat (Skype or Google Hangout). That's a good, safe way to make sure the guy is real, and to get a better idea of what he's like. If that goes well, arrange a date in a public place. Try to have fun, but take some safety precautions too. Arrange some check-in phone calls with someone, and make sure they know where you're going and when to expect you home. You might want to give them the guy's picture and info too. It's almost always overkill, but your safety IS important, and if you take these steps, then once on the date, you can relax more.
Don't expect a Pretty Woman date. A good date is one where you have lots of time to talk to each other and be comfortable, not one where he's showing off where he can take you and how much he can spend. Beware of those guys.
Ask plenty of questions; your main job is to check for compatibility, and also to have fun. If you aren't having fun, don't accept another date with the guy. If you are, then you're in good shape.