User blog comment:Starofstar/Confusion/@comment-13488655-20140414143436

It really depends on what works best for you. Some people find it easier to write a OCs story first to mold a characters strengths and weaknesses, while other find it easier to write the strengths and weaknesses first and then write about how the person came to have that personality.

(Personally I suggest the first option.)

After you make your OCs strengths you can look at them to see if they cover each others weaknesses. That might help to see if they make a well-balanced team.