The way the questions are worded tells me a little something about your intent and I cannot say it is something I am interested in entertaining. You're asking which words to include into your posts in order to accumulate merit; that is one of the single strangest questions I have seen so far regarding merit. I suggest you become genuinely more concerned about contributing to or benefiting the community in anyway than you are in receiving merit. Once you have accomplished this you will be in a much better position to warrant a positive reputation, merit points and all o' dat clout. 

I'll go through these questions directly, quickly.

Posts worthy of reward would be a post that is something along the lines of being any one or a combination of informative, beneficial to the community, or entertaining to an extensive degree. That's the best way I can think to word it, right now. It should consist of the aforementioned qualities. There has been thousands of posts from members of all backgrounds and ranks giving their opinion on what constitutes a merit-worthy post. You should use the search function, as it will give you exponentially more information that staying confined to your own thread.

There are no magic words.