The number of posts needed for the ranks are as follows:
Active Member 1000,
Resident Member 2000,
Resident Expert members is bestowed upon members who demonstrate scholarship (and typically formal training) in a field - often scientific (historically BioWizard has been the one to give this title, but we welcome nominations).
Same applies to Forum Moderator and Forum Admin. As for the other titles (with the exception of Banned User, of course), they are automatic, by post count.
Honored Members are our dearly departed RIP