1) The market is over-saturated 2) Hold contests for members 3) Work on SEO 4) The market is over-saturated 5) Create a rewards system on the site 6) The market is over-saturated 7) Have valuable content
You should read the Tips For Forum Owners first. And to get members to your forum without hiring forum posters, you will need to do lots of hard working for your forum. It is not a bad thing that you are not hiring forum posters but in that case you need to search and put really nice and useful info yourself and it is time-consuming. Just keep working on your forum for at least 3 months and then you will start seeing some result of your hard working
Hmm i would like to tell you that i worked on one local forum (game forum). First 20 users were friends and than we organised a counter stirke tournament, in the next few days forum had about 100 users
What I did was: first go on social type of websites (Twitter, Facebook, Youtube etc) and announce that forum to your friends and followers... on your forum make referral contest and offer some prize for top referrals.... what you will get is: people will do promotion for you to win that prize... of course, prize need to be interesting, but you will also need to offer something interesting on your forum to retain all those new members...
I'll be honest with you and say that I don't think anyone is going to post on a forum for a $2 .info domain.