Couple things. One is a light coating of talc power inside the tire lets the tube move a little freer. Next if this is a new tube after you have the tire one side on work the tube in and get the valve stem out the rim and slightly in flat the tube, this helps push the tube in place in the tire. Then let air out of the tube and carefully work the second side of tire on the rim. Check by pushing in on the sidewalls to make sure the tube is not going to be punched between the tire bead and the rim when inflated.
I'll know how good these ideas are in a couple days as soon as the new tires and tubes get here for my XS400!
drewpy, you must have been typing at the same time I was!