You won't really need any until about 10:00. For Magic Kingdom, you might want something like 10-11, 11-12, 12-1, because there is a good chance of getting 4th, 5th FPs for rides where the FP could actually save you some significant time in line.
For the other 3 parks, chances of a useful 4th Fast Pass are pretty slim, so you could set up your FPs for later. The hours between 1:00 and 5:00 will be when lines are the most horrendous, so during the afternoon hours you either want to be using FPs, watching shows, shopping, swimming, or napping.
At Epcot, the only really useful FP is for Test Track (with Soarin closed), and I'd recommend doing it before 11:00 when World Showcase opens because there's no way you want to trek all the way back to Test Track (or any other Future World attraction) while you're doing the long, long, walk through World Showcase.