I have 2 Pet Information sheet that I use at all M&Gs, one for boarding and drop in visits and one for house sitting. They both have dog/owner info at the top and has questions about the routine of the dog (feeding, walking, etc), any meds or allergies, behavior issues, etc. It has a space for alarm codes and other entry information. For house sitting, there are questions about alarms, how to operate kitchen appliances, TV, pool/spa, and other household items, will anyone else be entering the home (housekeeper, children), and location of nearby restaurants and grocery stores. I write everything down - my memory has never been that good, and the older I get the worse it gets :-)
I like to make notes after the meet and greet is over. I just want to have a one on one situation with the owner and the dog. It usually isn't long, I suggest to the owner that the send me notes of specific information. That way it is in their words and not mine. Most people are happy to do so.