The success you have on online dating sites will depend in large on the type of profile you've left for others to see. It should consist of an attractive picture as well as information about yourself. Information about yourself should include your age, location, marital status, interests and what you're looking for on the sites (friendship, relationship, commitment, etc.). Many online dating sites have a whole process for filling out a profile. In fact, it's the first step they'll take you through upon joining the site.
Keep Profile Active
The mistake many members make is putting up a profile and then forgetting all about it. For the first week or so, they sit around waiting for interested people to contact them. When that doesn't happen, they move on to other things. What this results in (besides little success in meeting someone) is your profile being pushed to the bottom of the pile because of inactivity. You may also want to login to your site to update it as well. The more you login to your site, the more it will show as active so you'll stay on top and get more views.
Initiate Contact
If you're a woman, keep in mind that gone are the days where only men are allowed to take the initiative. If you see someone that interests you on the site, don't hesitate to contact them. Whether it's a man or woman, they're on the site for the same reason you are. You may not think there is anything wrong with sitting back waiting for others to contact you. However, what if thousands of others are doing the same thing? How many potential friendships or relationships are you cheating yourself out of by waiting around?
Make Many New Friends
One of the great things about online dating sites is that it will show when you and others are online. This means that if you send a message to someone, you won't have to wait days to see if you got an answer. In most cases, you'll get an answer almost instantly (unless the person is not sitting in front of their computer). This will give you an opportunity to chat with others or message back and forth. Don't limit yourself to only one or two people, even if it seems like you've found exactly what you've been looking for. Talk to as many people as possible so you have many choices available to you. After all, you signed up for the site to meet new people, so make every effort to meet as many as possible.