How about titles like
1. Newbie : Brand new members who don't yet have PM privileges and who have not made many posts.
2: Regular Member: Someone who has PM priviledges and has shown that they are participating in discussions and contibuting in positive and helpful ways.
3: Dedicated Member: Some one who has been a Regular Member for a while and has been seen to be regularly mentoring newer members
4: Advanced Member: Has been a Dedicated Member for a long time, a long time user of the software and the forums.

Also going up in ranking should be based on number of posts and behaviour and bad behaviour that results in infractions should also result in lower ranking