Hire actual Members to write posts focused on keyword related questions that perform well in competitive Google searches. Depends on what your forum is all about, but lets say the forum is about home improvement.
Carefully construct thread titles using common language that accurately reflect what words users are using, such as "Can you paint latex over oil base paint", or "what's the best primer for drywall" or "how to tile a backsplash". It's not enough to have "posts", you need to have posts that compete well in Google search results. I'm using home improvement because over the last 2 weeks I've realized how abysmally piss-poor the entire niche is for providing good-quality data when I'm searching for it.
I could write on & on about this, but suffice to say that if I had the time & inclination, I'm pretty confident I could dominate the home improvement forums niche, because everyone else is doing a really poor job of it. Here's one nugget I've learned, and something to look for.
Take, for example the question "What's the best primer?" You'd think it's a common question, right? You'd think there'd be TONS of sites that had threads with that title, right? Fck no. I went looking for substantive information and the best I could find on page 1 was some mid-grade forum, in a thread that had a title that didn't even have anything to do with paint, but on page 3 of the thread, post #5, some guy asked the question using the exact same wording as I entered in the Google search. So, I'm thinking that if Google delivers mid-quality forums, thread not relevent, page 3 results as the 4th result on page one, then a thread that is titled with that exact question, word-for-word out to easily hit #1 on page one, right?
So, here's the "twist". Different members, different threads, same keywords, but each thread is titled slightly different. "What's the best primer?", "what's the best primer to use on drywall", "what's the best primer to use over oil based paint", "what's a good primer", "Is Zinzer primer good?", "Is latex primer good", etc... Keyword analysis should show which searches get the most traffic, but a thread titled with each of these ought to rank well, and then the substantive content in the threads might encourage visitors to join. Point is don't waste your time with non-native english speakers doing comment spam. When I'm searching forums, I drop the whole site the minute I see this obvious attempt at manipulating. Some of these people love to post, and so paying them even $1.00 per good-quality post could get you ROI. Or not. Obviously there's risk and the great unknown. Depends on your niche. Depends on you too. Most of the people here, attracted to "black hat", really internally translate that to "get something for nothing", and would look for a way to cut the corners of the corners that were left after they cut the corners off.
I'm currently toying with a forum idea, and what I intend to do (if I do) is to tie my "prepared" forum posts to certain current events with the idea that when people go searching for certain keywords that are still relatively new, my forum's post would rank well. I don't want to say any more because it's still on my "possible" list. But the idea here is to get your threads to rank well by using a "shotgun" method of having multiple threads with similar, but different, titles.
Another way is a method I haven't tried yet (adding this on as an afterthought).
So, everyone knows that Torrentfreak "scoops" everyone online with news related to P2P filesharing, right? All good, right? Can't beat Torrentfreak, right?
Wrong. I think I can beat TF, because TF writes for a 14 yo mindset. Their opinion is shallow, they lack a substantive legal perspective and their comments sections are truly the worst of the worst. And their commentors are truly bad too. I'd feature the best comments (even if I had to make them myself) on page 1, in reaction to my re-write of the Torrentfreak article (take the information, source it correctly, but present it much better, then offer better commentary, and then increase the quality of the comments in reaction to that commentary).
TF is fcking LAME and LAZY. Like taking candy from an infant. Sure, they get the best scoops. Where else would you send it? Then you run into wikipedia and the fights over whether or not TF is a "reliable source". Once you get "reliable source" credentials, wikipedia starts backlinking to your articles, even if you stole the information directly from TF.