I take along a phone, a tablet, and a cheat sheet with the high points for each shop. I skim the cheat sheet one last time before the shop, and afterwards write info on it for each point, e.g. time in line, # customers, whatever.
A tablet is a really good investment. You can put the guidelines on it and not have to print them, you can take notes on it after you leave the shop, you can fill out reports if you have them loaded, even if you have no Wifi. Even a 7" or 8" tablet is much larger than a phone and so easier to work with. You can sit in the parking lot at any number of businesses like McDonald's or Target and use their Wifi to upload or download. It's also good as a backup camera.