Make sure that the nosegear servo arm is on the furthest hole and the servo arm on the nearest hole. Im guessing the beaver is a nose gear so the nose wheel should turn only about 10-15 degrees each way. Its better to have the wheel turning to little than to much. Dont apply to much rudder everything must be slow smooth and gentle (man how many times have i heard that). Also try mounting your wings on. My guess is it will probably balance your plane more and giving more weight thus more friction. The way a taxi my plane probably everyone does it like this (not sure) is apply a little throttle then pull back a little apply some more then pull back to idle. (Making sure not to stop your engine). Ive only taxied about 7 times now and i find it really hard when theres stuff on the runway (epecially in Canada with all the snow and ice). You got to apply up elevator when going over bumps or whatever but this usaully messes me up and i lose control. Make sure your nose wheel is perfectly straight and your rudder to. About controlling the plane as a complete beginner i find that in the air as long as it is not too far out of sight it is easier to control in air than on ground theres no obstacles in the air exept other planes (but i only fly when its only me out) but of course it all depends how smooth your plane flys.

Hope this helps,

Papa