how do i join and which is best?
Which campaign is best very much depends on how often you post, where in the forum you post, and the campaigns available at the moment.
If you make less than 50 posts a month, Bitmixer.io might be a good choice; there are no minimum post requirements, and you receive up to 0.01 btc per week. If you make between 50 and 100 posts a month, you might want to look at a fixed post campaign, which pays a set amount of btc for a set number of posts (for example, the LuckyBit campaign, GawMiners, FortuneJack, and so on). If you make more than 100 posts a month, you might want to join a pay per post campaign like Pocket Dice, or maybe wait a little for PrimeDice to return: in these campaigns, the more you post, the more you get, but they typically pay less per post than the fixed post campaigns.
After you decide which campaign you want to join (looking at the OP might help here), go to the respective thread, check if there are open spots and the relevant campaign rules, and post your entry details there.
EDIT: bitcoininformation beat me to it.
