State of the carpet, especially if they have pets - is it wearing really quickly?
Is all plumbing working as expected - faucets/spigots all turn on fine & drain, don't leak
Status of the yard/sprinkler system
Look for trip/accident hazards around the exterior (shifting concrete, etc.)
Take a look at the roof, check for missing shingles, clogged gutters, other problems
I imagine a lot of tenants would report when they have problems with various things, but some don't - so maybe make it clear to every tenant that you'd like to keep things nice and fixed up for them, and ask at your inspections if anything is wrong - as a tenant I've had grout fall apart in a shower, a window stop latching, drawers in the kitchen get wonky, towel bars fall off the wall, etc. Little things like that you won't want to check manually every place, but you could ask them to think really quickly if anything like that needs to be fixed up.