you make the attractive offer to you visitors it is the only way which help you in the increase the visitors
Having people's friends already there is a big bonus. But seriously, unless you're going for a very specific niche then you're going to have a really hard time getting a Facebook-like social networking site up and running with any degree of success.
Provide something useful to people to sign up on your new social network. You must also make your social network design attracting and user-friendly. The signing up process should be also easy, simple and fast so that all internet users can easily sign up even those people that are not techy.
There are several options depending on many factors including your niche, if it's free or not, and results expected. Having a free membership is easily the most obvious way to gain more members. If your site is not free than you may want to consider PPC. PPC is the quickest way to get exposer, but results will vary on experience, website, price, and other details. If you go the PPC route, hire someone or read up on it first. You can always test while reading. What does your social network have that's different. You need to make this known and voice it on the front page. Another option is use video marketing. Tell people the features and show them how easy it is to join, etc. Think outside the box and just work hard at it.
You must make your site attractive and interesting, then to try to do some link building efforts on it.
Keep your profile active by announcing contests, asking puzzle , attractive status, game application etc.In short you should build your status social network which ultimately attract people to join you...
Creating interaction with your posts is always important. Create posts that provoke a response of follow up post by your fans. Example are creating posts that require reader to comment. "What do you think about this blah blah blah ?" the responses will get greater exposure to friends of your friends by increasing feed exposure