I had a peep at your forum...well it's not so busy but not to worry.
I would suggest the followings:
1) Get some of your buddies/friends to join as mods for a start to make the forum more lively and interesting. I am sure you computer literate guys have a lot to talk and with your tech knowledge
2)Maybe create a section for news on the latest design on hardware, and software for newbies/pros, it will attract more people to join in or search for some interesting thing or keep up to date with the lastest in the market products and repairs.
3)Well, you got to try very hard to get listed on most search engines and portal sites to be known and it may work.
4)Use some brain-storming sessions for ideas with your mods/friends in getting more members and making the forum more busy might work and also work out the ranking title if possible with them.
The above is just the tip of the iceberg, please search and look for more and also similar forums and what makes them popular.