I myself met my current girlfriend online. Not on a dating site, per se, but on World of Warcraft. We were online friends for a few years before we 'leveled up' our friendship, but it still counts, right?
There are so many dating websites out there, ranging from religious to ethnic to political and beyond. Some of the best dating sites are so crowded, you can easily get lost in an ocean of 'fish in the sea.' So what is a single person to do, when you're ready to mingle?
Firstly, be honest. Why?
...I wonder why...
Secondly, go in with mild expectations. If the statistics are true, 1 in 4 couples met each other online. How many of those lead to marriage? A long, happy marriage? You may or may not find your soulmate on an online dating site, but you never know.
Lastly, do your homework. Most online sites, especially the best dating sites will charge a membership fee of some sort. Think of this as not only an investment of your time but also actual money. I personally don't like throwing $20/30/40/50 away on a whim, and you shouldn't either.
Once you have a plan, stick to it. Be consistent. If things don't work out the first time around, keep plodding away. If you're one that reinvents themselves after every failed relationship, you're probably never going to find a true match.
Best of luck. I got lucky, and found an amazing friend and partner online. Bonus points for her being a hot gamer chick. You too can find a match! They're only a click away! (or something...)