Ways to keep members active

Give them incentives, that is the main thing. In the beginning it will be hard to keep members active, so give incentives to want to stay active. The best thing is to hold contests that are fun and interesting, whether they have a killer prize or not, it is always fun, and everybody likes a little competition. Another big one is to offer something unique, something no other forums have, that will make people want to stay active because you will have something the other forums do not have.

That's is extremely correct
The main thing a forum should be build around is unique content

A contest always creates a buzz, the thing I have seem on IF forums is the contests have some sort of domain up for grabs.

Yes, Im going to think of a contest to do on my forum

Yea, domains are a typical prize, people get tired of them being prizes after a while.

New topics on a regular basis, particularly topics that promotes discussion, are a very good incentive. It can quickly get difficult, but it's important, and it pays off. On big forums that don't rely on word-of-mouth, the membership is self-sustaining in this respect, but for word-of-mouth forums, this incentive is very important for the admin to help a lot to give.

well, i'll be up and waiting for your first contest. i think all you need to keep members active is member's imagination. if one makes a great thread than all will come and comment that. like that, you earn more and more users and you keep old users active. it's also nice if you create interesting rankings that depend on how many posts each one has done.

One more way to do so is to give free stuff to the persons who make fast responses to the threads!!

In this forum that would go to Ibill
I just finished the thread and that guy replied to it..great help buddy!!

Haha thanks, that's what I'm here to do.

But the problem with that idea is that members would then just be responding to threads without reading through the posts and giving a good answer, or response, to the thread, just for the prize.