Tradrick, I go by sound and the feel of the wood when working it and by the resistance when bending(don't over stress it). This comes with many years of experience though. You can use a moisture meter but the pin type meters will only tell you what the M/C is as deep as the pins go.
Under the dry winter conditions, 6 weeks or so will be a good starting point with a stave that is at almost bow dimensions. Even if it is not completely dry you can take the bow to floor tiller stage(about 4" of bend) without over stressing. At this point, it will dry even faster. When you speed up the drying of a bow stave you will probably find it will increase in draw weight over the next year or so as the wood cures.
I also like Ryan's dimensions. After you build a bow with these dimensions you may be able to adjust the design on the next bow. Pat