Most of the basics were covered - slope flooding, inspections, etc. The slope thing alone caused me to walk away from a property we were considering last year.
But here's the biggie:
Neighbors... Look at the neighbors. Make note of the condition of their properties and yards, see if there are renters in the area, etc. Check to see if anyone has three ATV's parked alongside the garage, etc. Now, I mention renters not because I have anything against them (most of us were renters at one time), but because rental properties in a residential neighborhood are usually a pain. You never know when three college buds are gonna split the rent and have parties every Sat night. If you are looking in a place where renters will be (like a townhouse development, etc), see if there's some kind of homeowner's association or rules against that sort of thing.
I've known plenty of people with bad neighbors - there is almost nothing worse. Now, you can't control who moves in after you, but you
can control who
you move next to. If you like to smoke weed on the back porch (I know you don't, Jen, but it's an example) don't move next door to a cop.