Find out the ages of the house's components - How old is the roof? Water Heater? HVAC system? Appliances (if they convey)? If one or more are very old, consider that fact in the price negotiations that they will need replacing possibly not long after you move in. Roof and HVAC System repairs/replacements can easily cost you thousands. Also consider the driveway (if there is one), is it gravel, asphalt, tar & chip, just dirt? A basic front yard asphalt driveway, if you need one put in (or just really want it), can easily cost you up in the $2500 - $4000 range. The other options mentioned are of course cheaper.
As someone else mentioned, the slope of the property and the comparable elevations of the surrounding properties. Generally, comparable higher elevation = good, lower = bad. Lower does not necessarily make it bad, you just need to be aware that water will always run downhill, so make sure the property has a dry foundation and proper drainage (or can have drainage put it in relatively cheaply). <-- This was an issue at my current house - I knew my house had water issues due to it being at a lower elevation in the neighborhood, but the foundation was solid and dry. So after a Spring of putting down plenty of grass and plants, improvements to the gutters, and putting in a drainage system (underground percolating pipes and a couple french drains), the water issue has been mitigated (though after a heavy rainstorm it's still best to avoid the backyard for a couple days). Additional note: if the foundation is not dry, or showing serious signs of stress/cracks, it's probably best to move on from that house - no matter what anyone (seller's agent) else says. This also goes for large cracks in the interior walls/around doors/windows - it could be signs of settlement issues (all homes will experience some degree of settlement though).
Related to the slope/elevation issue - if you're on city sewer (not septic), and on a low elevation, ask your home inspector about the angle of your main home sewer line to the public sewer line. If your main line is significantly angled UP to get to the public sewer line, just be warned you might be facing a huge issue if that thing ever became plugged/broken. There are ways to mitigate this, but few are cheap.
Did the owner's recently put on new vinyl siding (or other siding)? Ask a pest control expert/home inspector to please to check for obvious signs of rot/pest infestation underneath the siding (if it's vinyl this can easily be done). Some people aren't above going to extremes to hide expensive fixes (even with expensive fixes).
Use a home inspector you feel good about, my home inspector came highly recommended from trusted friends - he ended up catching multiple "soon-to-be-big issues" I never would have caught, and swore he would not pass the house unless they were addressed - motivated sellers quickly fixed those issues.
If you're not in a hurry to buy a home (you shouldn't be in a hurry to make such a large purchase/commitment) consider waiting until the fall/winter (but by all means start looking now). The market may be smaller during the fall/winter, but if you find a house you like during that time chances are the sellers are more "motivated" than Spring sellers. That, plus few yards look better during the winter than during the spring/summer, limiting curb appeal. All this to say you can usually knock a few thousand off the home prices during the fall/winter.
That's a few things that I know I had to consider/deal with.
