Dear all,
I am thinking of setting up my social networking site with idea of attracting relevant users and so I have decided to add invite only feature, so there will be no open registrations on my site.
Idea is I would like to distribute invitation codes such that user can register with them.
I need some idea as to how to distribute these invitation codes using social media, such that it can be fun. I know almost all of these social website these days supports apps, widgets etc. I need to have some online poll, campaign and later will distribute some codes. One plan is to do offline as well, like actually going to field and meet target groups and distribute them flyers and registration code.
I would like to know whats the best way to go about it online? I am planning to allow 1000+ user register first and see how it goes. Its quite some time before I can launch my site but i need to have it planned now.

Any idea will be appreciated.