Before you can hope to motivate employees you must understand their hierarchy of needs.
Employees will not develop a need for things at the higher levels of the pyramid until they have totally satisfied their needs at lower levels. Make sure they get plenty of the stuff on the lower levels, but not so much that they develop a need for more money.
(I got this in paper copy from co-worker TheShark and thought it was worth recreating for the internets. We agreed that we mostly live in level two.)