Get a better posture
Image The posture of the pianist
1.Sit deeply at the chair.And make a muscle along the spine straight.
2.Draw keyboard near your body.
3.Elbows angle must be right_angled(The weight of your arms tired yourself).
4.Make your fingers round like having a egg.
5.If possible,it's better not to put your arms on the desk.
Pianist is always playing a piano without loading down anywhere with the arm.
If you get tired,you shoud put something under your arms.