A big one I didn't mention is having a search comment. You should always go in and edit your seach comment with your TNL and other such stuff. People tend to invite the people with a search comment first. Putting in your comment that you have WHM and BLM available will make people wanna invite you more because they'll assume you have more experience in the game. Also the higher you go the more you might need WHM sub for main healing where you absolutely must have things like Paralyna etc to main heal.