How to get advertisers on my PTC site..??

Hey people!

I have recently started my own PTC site HOWEVER!
How do I get advertisers??

I mean, if you don't have ads, users won't join!
And if you don't have users, you won't get ads!

So how did sites like Neobux and so on, get advertisers to use their site?

Thanks for any tips you can give me.