I have also searched so much for this question because I was not able to rank up when there was still no merit needed, and i have learned that most of the merits are given to "quality posts" that are posted by knowledeables who are usually high ranking in bitcointalk. Mostly are links or articles about something important in crypto, so maybe Ill try so follow same path if I'll get some merits too.
One other thing, I have read in the meta that soliciting merits from users could be bad for you, so dont.