Find the best bounty program that is listed in bounty section: https://bitcointalk.org/index.php?board=238.0
Wear the appropriate signature and start posting in the forum on various boards, involve in discussions. At the end complete the required number of posts and it'll be calculated by the bounty manager and you will be paid after the completion of the bounty campaign.

I will also recommend you go for this, as this fella has done well to explain in simple term how to really go about things pertaining to signatures campaign.

However, I will also like to chip this in; that you have must carefully observe the aforementioned, do well to come observe well which campaigns you are  gonna be joining to henceforth cos so many crappy ICOs are outta there.