Artak is right. There is no "how to become a moderator". You can apply for most positions in OFPEC, but not for moderator. Being a moderator comes with considerable powers and experience tells us that people who don't ask for these powers are most suited for the job. Thus, asking to become a moderator is rather counter-productive.
Keeping the forums nice and peaceful does not only require a certain amount of responsibilty, you also get nothing in return than occasionally being offended by people for just doing your job. That's why we don't want people who want to be moderator because it's cool to be one or because they simply want the powers. The best way to prevent this is to hand-pick our moderators.