They say the easiest way to earn merits is to post quality post. I don't find it very helpful. Most of the people here don't care what others are posting and not that kind enough to give you merit even once. No matter how good your post is, you will barely recognized.
True that, lot of good and helpful posts just stay with 0 merit so there is no reward for being a nice guy. A best way is posting funny and sarcastic answers.
I just realize that in meta section:
https://bitcointalk.org/index.php?board=24.0 ,there are some very nice members they would like to give us some merits, but we need to convince them by providing very helpful posts. Actually if you could make some funny post, it should be nice. But if you could make something helpful, of course it's better, today you may not get any merit, tomorrow you will get it. Today I read 1 interesting post about his rank's up (from full member to Sr.Member, of course it's not easy) after merit system was implemented:
https://bitcointalk.org/index.php?topic=3166903