In-game there is basically… Ask your clan: And that’s it…
And it kinda sucks because that being the case your best option is just join the biggest zerg clan you can find which gives you the biggest pool of players to potentially level with greatly increasing your leveling speed…
But if you want to form a clan for any other reason, say a group of RL friends or a guild from another game… then you deny yourself that pool of players and basically resign yourself to only ever playing solo at a much slower speed.