Jeremy, I have written a couple of articles on this topic in the past but can't seem to find them right now. Here is my quick list:
1. Check the SERPs (this is critical) -- is one of those IYPs (IYP Categories) showing up for your targeted keyword phrases organically on Google, Yahoo, or MSN. You can benefit from organic IYP distribution.
2. Regionalization - IYPs are used disporportionaly on the basis of geography. Who is your phonebook provider? You should direct dollars to the regional bell operating company that is dominate in your marketplace.
2. Category density - how dense is the competition within particular categories. If your ad is going to show on page 2 or 3, forget about it. Try to locate categories that might have been overlooked by competition.
In my opinion, you should forget about the following for a paid listing:
And in terms of choosing between RealPages, SmartPages, DEX, and Superpages, consider my second point. I don't think for example that DEX has much users in Dallas.
AOL, Switch and YellowPages.com are national players - switch and yellow in particular represent affordable inventory and there are some deals to be had on yellow right now with Smart and Real distribution (merger). Switch for the the past couple of years has been by far the most effectively placed pure play IYP as far as organic distribution is concerned. Again study those serps.
AOL and Super YPs are excellent properties and should be considered amongst any shortlist. Super acts much less like a regional iyp and more like a national search engine these days with multiple buy types including ppc and a pure search environment.
Why did you leave out Y!YP?
There is a few more points, i will try to gather up more later.