I have played the piano with tension in my hands/arms/shoulders almost all of my life and only in the last ten years or so have I learned to play with [almost no] pain and with much more freedom. My path to proper tone production was this: 1) a teacher my senior year of college who shared with me that "certain passages can be played more easily just by turning your hand a little bit" - the first I'd every heard of that - a thinking/planning approach! 2) a teacher after college who had been taught by Tobias Matthay and took me through the various short exercises Matthay had written [some of the previous posters talk of these types of exercises], 3) my most recent teacher who was patient and stubborn in my playing with quality tone [impossible if the tension-less technique is not employed] and finally, 4) coming down with severe tendonitis from overuse of my hands between a typing job and a church job. To recover, which took six months, I (a) rested, starting with two weeks of no playing the piano at all, (b) stopped doing the typing job, (c) learned how to self-help-massage the sore tendons in my arms and shoulders - my tension was actually starting in my neck and shoulders, which, for me, resulted in the forearm/wrist/hand pain, (d) took ibuprofen [an anti-inflammatory] as needed, (e) kept hydrated, and (f) played easier music, if and when I could. One warm-up that helps me stay tension-free now is playing one hand's part between two hands, just taking my time and feeling the upper arm being the lifter (which causes the wrists to lift naturally).