Learn to give now. Many people say that they will give more and serve more when they become rich. They want the miracle without having the faith, the fruit before the seed, the reaping before the sowing. But faith must precede the miracle. The prophet Moroni commented on this idea:

And now, I, Moroni, would speak somewhat concerning these things; I would show unto the world that faith is things which are hoped for and not seen; wherefore, dispute not because ye see not, for ye receive no witness until after the trial of your faith. (Ether 12:6)

Decide now to give. I recommend that you think about putting your giving in percentage terms. Learn to give a certain percentage of your income so that you will never truly change the amount you give (except, perhaps, to give more), no matter what your income is or what you are blessed with.