If you're looking to make bid giving more selective you might want to think about implementing values based membership selection (VBMS). So instead of saying, "Oh I liked this guy" you could say, "This guy should get a bid because he exemplifies X, Y, and Z." X, Y, and Z being qualities your chapter values that are measuarable and quantifiable. The idea behind VBMS is that you can actually measure the quality of your pledge class (an in turn, your chapter) because you have a rubric by which you give bids. To make this work your chapter has to agree that a man can't get a bid if he doesn't exemplify a certain number of the qualities defined by the chapter.
This is a really good article about VBMS that probably explains it a lot better than I could:
http://www.phiredup.com/index.php?op...p=587&Itemid=2