You'll need to start a viral campaign. Is there something special or cool about yours that no one else is doing? If so, try to find a way tog et people excited about it. (If not you've got an uphill battle anyway and should try to identify why people should choose you over the big guys).

The biggest thing with marketing a new site, especially one with a lot of competition, is to be able to answer the question "If I did not own this site and stumbled across it, would I join it?". Why should someone choose your site over the likes of your competition? What do you do better or do you offer something that your competition does not. If you have a site that is a replica of an already established community you will find it very hard to convince your visitors that they should visit your site more frequently than your competition.

What's the name of the website and domain name?

Depend on what type of users you are going to focus, if you can be able to attract more and more users, you will find it easier to make it viral as users themselve make things viral and rest the technology do itself.

i think it would be really hard to make the site work. there are so many big competitor out there with the same concept.

The persona of “popularity” of a social networking site can be achieved by recommendation and referring others and rest the technology do itself.

I use some social networks. I think you have to have your own unique features to attract more users.

Having a contest will definitely be a good idea. When you give away something free people will come.

I say come up with something tangible to give out and post your contest around forums.

Contests are difficult to use as you have a problem: how can you get people excited about your content when you don't have people at your website? If people don't know about the website they won't know about the contest. But once you have a lot of people at the website then you don't need the contest anymore.