Participating in signature campaigns requires you to impart your knowledge in multiple areas. Generally, these campaigns require you to post "x" number of times in a given week. If you are able to meet the required quota and other stipulations, you are rewarded weekly with a payment of BTC, which increases as your forum rank gets higher.
Of course, the competition is significantly tough in these campaigns as there is no shortage of good and quality posters coming daily.
If you truly want to participate and at least get a competitive edge among your competitors, you must be able to possess a good post quality. This includes your grammar, construction, and other knowledge in the cryptocurrency field that makes the manager choose you as their participant.