Well the advantages would be having people to play in fire teams, strikes, raids, crucible teams and etc. There are certain achievements in the game you can only get by being in a clan. Also I've heard that your clan may be able to get a specific "shader" for the members in the clans color scheme. To join a clan you basically join a group here on bungie.net (just click on the groups tab to the left) or just click on the clans tab and search up a clan that you might want to join. A good place to look for clans is the clans section in the forums. Hope this helps P.S.- What console are you playing on?