To avoid muscle soreness and fatigue, don't hunch your shoulders. Tilt your head every few minutes to stave off tight neck muscles. Better yet: Stop to admire the scenery.
Don't move your upper body too much. Let your back serve as a fulcrum, with your bike swaying from side to side beneath it.
By sliding rearward or forward on the saddle, you can emphasize different muscle groups. This is useful on a long climb as a way to give various muscles a rest while others take over the work. Moving forward accentuates the quadriceps, while moving back emphasizes the hamstrings and glutes.
If you're not comfortable taking both hands off the bar, after pulling an arm warmer down with the opposite hand, use your teeth to pull the bundled fabric the rest of the way over your wrist and off.