I think it is also safe if I advise everyone whose targets are to earn merit to try and niche down their interests to few boards. Maybe 3 to 6 different boards in the forum. Depending on how vast you can be and how easily one can diversify. Sticking to few boards will help you to become more familiar with the FAQs in the boards and learn more about specific topics as well as meaningful discussions.
My mate above, talked about reading more and working harder to improve your vocabularies. I will also say reading more will get you more acquainted with the terminologies of the topics in your board and will give you the know-how to be able to answer questions, in-depth. In every face of life, you need to work hard to attain mastery and it is not advisable to try to become a jack of all trades and master of none. It is actually great to have deep understanding of few things than having few understanding of various aspects. It is one of the reasons why scholars popularize Quality above Quantity.
The merit system is design in a way that other members appreciate your efforts into solving problems. It is like a reward system for your efforts and it is advised that you create problem-solving threads in the forum to get more merits. Noteworthy of other things is your ability to answer technical questions from the technical boards.