Beginning on the day that you complete the purchase of a home, keep track of everything you spend on major improvements. You will need to document those expenditures, which increase your home's "basis" (and thus reduce your net "gain") when you eventually sell. Even with today's liberal capital gains exclusion, rapidly rising home values may push some homeowners closer to the taxable gain threshold faster than they suspect.
If possible, take photographs of each house: the outside, the major rooms, the yard, and extra features that you like or ones you see as potential problems. And don’t hesitate to return for a second look.