How many groups can I join?

It depends on whether you join as a Member or Administrator. Every deviant can be a Member of an unlimited number of groups, but can be an administrator of only three of these groups. Premium Members can be an administrator of up to 10 groups.

But, keep in mind that making a group is considered the same as joining one as an administrator. (When you make a group, you join the group as a Founder, the highest administrator level). So, if you're already an admin of another group then you can make up to two more to reach your three limit. Got it?