From my observation, it's not really that hard to get your first merit and it does not always get easier from then on. Some members are lenient to newbies and would merit them for effort, even if they were wrong or it was just an inquiry. If a new member is posting useful content and not just spamming the forum, they would eventually get noticed.

As you rank up, so does the standard other members hold you to, so it could become harder to get merits if you do not equally improve your knowledge on topics you discuss about. Some members also simply target a particular rank and stop putting effort into their posts from then on.