There are 2 main factors that I have always used. 1. The course determines my club selection. Some courses you can get away with 4 wedges, or sub a hybrid for your fairway wood. The 2nd factor for me is the wedge has to meet my needs just as much around the green (chipping, Pitching and Flopping) as much as it does on those shots below 100 yds. I carry the ZSatin 98, 77 and 50 yd wedges. Some like the Cleveland wedges and thats great, just to much backspin for me personally. But this is what I like for others it may not be what they like. I have found trial and error as well as seeing what others play helped me determine what I currently use.
As a add on item, the ball you use makes a tremendous amount of difference in how you play your irons and wedges. Again, it all goes back to what YOU like...