It may not sound like good advice, but date as many people online as possible and keep dating offline too. In other words, don't put all your eggs in one inbox. Jim Buckmaster, the CEO of Craigslist, says that the advantages of online personals are that you're "able to learn something about hundreds or thousands of partners and weigh one against the other on all kinds of criteria."
There's also no need to limit yourself to one dating site, although I'd say it's a little creepy to have more than one profile on the same site. Soon enough someone will discover that you're both NYAccountant2007 and HotRocknRollDude, and your multiple personalities will make you look disingenuous.