In my travels I almost alway get off the interstate and look for the smaller roads going through small towns. I think it is inspired by the book Blue Highways by William Least Heat Moon.
In any case I often look to create a photo project for a trip. A few years ago I photographed ice cream stands across the country. It turns out the whole country does not have ice-cream stand or most have been replaced by the corporate giant Dairy Queen, not so interesting. Somehow I recognized that just about every community in the US and around the world has public buildings. I chose the post office for this ongoing photo project. When ever I have some spare time on a trip I will look up the local post office. I like to search for an image on Google maps. If the post office is newer, I tend not to go by and shoot it. I look for the old and unusual or spartan. I have seen post offices in the smallest buildings, attached to homes, out in the middle of nowhere and large central offices in the middle of larger cities.