One simple very effective rule in this community is NOT to ask/brag for clan invitations and try to apply yourself or wait for an invitation.
Applying also has its rules depending on the what-based clan. (ingame-based, irc-based, art-based, forum-based, skill-based)
And also requirements such as: skills/belt/etc.
Just NEVER ask/brag to get automatically invited into a clan without showing any effort.