As a new forum owner this advice is great but it is trial and error too - I have spent many hours promoting and getting my link out there, but its getting those members that join to post and remain active.

I do run monthly contests but the rewards and prizes are donated by companies related to the forum so it doesnt have to be costly. I think showing your members how you appreciate them is the key to getting them to remain with you, though its still a battle every day to get them posting and logging on.