There are essentially two ways to go about drafting your fantasy baseball squad. With the first, you decide which players you like and make sure, within reason, that you pay what it takes to get them. I'll call this the "genius" philosophy of drafting. With the second, you enter the draft without any idea what player you're going to draft/buy, and you simply take those who you believe are undervalued. I'll call this the "agnostic" philosophy of drafting. So which is better - the genius or the agnostic. Or more aptly, (since almost everyone combines the two to some extent), what's your split between genius and agnostic?
The genius philosophy presumes you can predict better than others which players will perform in the higher end of their expectation range. Why you believe you have this particular ability isn't important. The agnostic philosophy presumes that no one over the long haul has any particular expertise at predicting what end of the market-based expectation range a player's performance will fall and seeks to take advantage of those who mistake themselves for prophets.
Personally, I think I'm about 60/40 genius - maybe even 70/30 - at least in an auction. I tend to target a bunch of big name players I like for whatever reason with half to two-thirds of my budget. Then I wait around forever for bargains as an agnostic, though even then I have strong preferences for players I have hunches about. In a draft, I'm more likely to be agnostic - taking players where they fall for the first eight rounds or so.