After climbing on the roof, I normally head toward the attic. One of the reasons is heat. On those typical, hot, Texas summer days, an attic can reach temperatures near 200 degrees! Personally, I want to have time to look over as much of the attic as possible, so it's best to get in there while it's still early in the day.
The structure of the attic can tell a great deal about the framing contractor. If I see sloppy construction methods for the roof structure, that may indicate the walls weren't framed well either; however, if good construction techniques are visible in the attic, that usually means the framing crew "cared" about providing a quality product. I do occasionally find a broken piece of attic framing or, in older homes, sagging rafters. These can usually be repaired with little fuss.
The attic also provides the best view for determining if leaks are occuring during rainstorms. I try to look around every single penetration (vent pipes, chimneys, etc...) for wet, stained or damaged wood.
Ventilation is another factor that is considered. One square foot of opening is recommended for every 150 square feet of attic space. Most homes fail here. One or two turbine vents are all that I generally see. Occasionally a home will have a ridge vent or gable vents. However, unless you are purchasing a home with the newer foam-sprayed insulation, you will want to ensure that your home "breathes" adequately.
Insulation should be compared to a sponge. There is only so much heat that your insulation sponge can hold. Once the insulation is "full", the heat has nowhere to go but into your home through the sheetrock. Hopefully the rest of the heat can pass back out through the ventilation openings. Becuase Texas has really hot summers, the recommended minimum amount of insulation is about an R-40. Whether the insulation is blown-in, batts or some other newer method, I want to be able to tell my clients what they should expect in the way of insulating performance.
If there is any HVAC equipment or plumbing equipment in the attic, I begin inspecting it as well. But I'll save that particular discussion for another day.