Let's pretend I have this forum and these are its stats

In total there are 1088 users online :: 880 Registered, 12 Hidden and 196 Guests

How much (in your opinion) should I charge for a text link or a banner ad per day?
I donno how much unique hits or pages views I get per day but looking for activity of that forum, it's gotta be alot.

I'm new in offering ad spaces so please advise.

Also please, can you tell me how can I make money other than placing ads on my forum/site?

Depends on what is your website's PageRank.

Also, you can charge users for text/banner places, paid newsletters, create closed forums with paid membership.

Charge for sticky threads.