Me personally if it's my boat I don't expect anything (I'm a little funny that way) and if I'm going with someone I just ask how much (again a little funny that way)
I fished with a buddy from work for 13years and can't recall a time when he asked me for anything and the funny thing is is when I got my boat and took him and another buddy fishing they insisted on paying their part 1/3rd each--again I didn't expect it nor asked for it but it was appreciated.