Few things we've learned over the years (keeping in mind that the time of year you're going effects pretty much everything)...
Lunch is easier to get than dinner. And some places lunch goes to 3:30 or 4, so you could call it an early dinner. The other plus is that some places have the same menu for both, but it's actually a few $ cheaper for "lunch" - especially at DTD restaurants.
Some resorts are easier to get than others. In particular, try some of the ones that aren't directly around MK/EP. Check out the menus section here to scout around for something that sounds good to you.
DTD restaurants tend to be easier than parks - especially during off hours. We've walked into Pucks any number of times with no wait at all (although this is tougher on the weekends)
Shoot for the "ends" of the dining window instead of the traditional meal times. Early/late dinners are sometimes easier to get than between 6-8pm.
Never hurts to try calling that day or the day before and seeing what's available. Cancellations happen... a LOT. I was able to switch a California Grill ressie from 9:55 to a much more manageable 8:00 the same morning.
We've walked into Restaurant Marrakesh lots of times. Never had a wait there. Food is good (love everything there - especially the lemon chix), although it's a bit loud.
Check out the restaurant listing at the kiosk in HS (right at the end of the main drag as you're walking in). We once walked up at 12:20 and got a 1pm for lunch at Prime Time.
