1) Take part in contests, for example, in 10th anniversary art contest there were tons merit being given away to participants (their work was good, no doubt on that).
2) Take part in giveaway threads, there were lots on Christmas and on new year days.
I miss to join those past 10th anniversary contest and merit is raining for people who joins but for now maybe the one I see the most effective to get those merit is helping the newbies in your local section since I think the competition for getting those merits is less compare to international boards where mostly the one who get it is those people who have huge reputation and scam busters but identifying scams takes to much time of work.