CMS proposes that the Stage 2 requirements begin in 2014, meaning that the Stage 1 rules are in place until then. No matter when your practice starts its efforts to attest to meaningful use, you will remain in Stage 1 for a two-year period.
Here's a chart to help you navigate your course:
Here's the payment (and penalty) breakdown for the Medicare and Medicaid programs:
(Chart information courtesy of the American Medical Association / CMS)