Instructions
Start your own clan from the ground up. If you start your own clan, you become the leader by default. Recruit other people into your clan by posting on video game message boards or by talking to people while playing online games. Identify yourself as the leader and make sure all new recruits understand that you are in an authority position.
Join a pre-existing clan and work your way up through the ranks. Members of a clan are typically promoted due to their skills within a particular game. If you are really good at "Call of Duty: Black Ops" for example, your clan leader will notice this and slowly promote you through the clan. You can eventually work your way to the top of the clan.
Stage a mutiny against the existing leader of a particular clan (if you feel you can perform the job better than he or she). Clan leaders typically choose who a particular clan plays against and what strategies they use. If you feel like you'd make a better clan leader and you know other members feel the same way, start your own splinter clan or get other members to only take commands from you. This will force the existing leader out of her position.