Nothing different compared to real life. You need to work for it of course. Offering your service in the Services section and demanding btc as payment is a good way to earn money. If you are exceptionally skillful in one thing, try offering that in the Services section.

Signature campaigns are also a good thing to earn some additional money. In here, you don't need to work that hard: posting constructive posts and being active in the discussion and the forum is all that you need to earn. Aside from that, there are frequent giveaways in here and bounties that are really fun to participate in. Don't seek for too much money, seek also for the knowledge that may help you earn the money that you're looking for. Well that's about all that I do in this forum to earn some extra money: post, participate, discuss, be active.