Sadly, "luck" is the word that best describes most merit give away threads
Its not about "luck" its about how well you write your response to a certain question/post. All post that have substance in it and is not repetitive get merits to the eyes of the ones reading it.
One should write at least 10 bitcoin-like whitepapers as posts in order to receive merit to become a member.
Nope, just be straight to the point (response should not be like an essay).
Seriously, it's not really fair to those who are newcomers, I read some threads where people have noticed that members with old accounts just create new ones and send them merit to promote to member. I really wish 1 merit was enough to become a member for those of us who do not have old alt accounts.
If you notice some, then try to investigate it. If your investigation came to a conclusion that the accounts are connected then you can get merits. To more about the details
go here.