I'd just say, if you have a Leadership score of 6, make an ECL 4 character for a cohort. If it's a 4th level dwarf barbarian, a 3rd level tiefling rogue, or anything with four effective levels, that's groovy.
Leadership is actually quite nice for small games. I've been in a campaign occasionally lately, and we three members of the party. If we all attract cohorts, we move up to six, although half of the party are cohorts, of course, but the numbers would really make a difference. We don't have any fighting-types, so if we all get fighter cohorts as soon as possible, we can have quite the meat-shield.