Does anyone have a good article, or a good idea of how to do a valuation of ratio categories? AVG, OBP, ERA, WHIP.

I have a basic idea, but in order to be more scientific in how i look at things, i was wondering if someone had a good way to look at how you evaluate these categories. It's very easy to see a players contribution in counting stats, but i've never had a full grasp of grasping the contribution in ratios. For example i never end up drafting ichiro.

Anyways, any help would be greatly appreciated.