One thing I try to do, but don't always succeed at is to pick being an admin first and leave posts for others to jump on. Generally I might leave a delicious post that I'd like to counter for an hour or 4 to see if everyone else will say what I might have.
One thing I find hard is that the threads I'm not interested in I don't follow closely enough to do a good job of admining. The ones I am interested in I get to involved in non-admin mode to be able to look fair if I start admining. That part is tricky for me.
I suggest than if you start having trouble with the keeping both modes separate you ask another admin to do the dirty work for you. I would hope that they would be harder on you than anyone esle .