I have shopped many restaurants with many different companies. I place a small note pad in my pocket book and put in the time of everything from start to finish. Only down to the minute, not the second. Most everything else I can remember. When I get ready to do the report I take the times and mark the minutes in between. Descriptions of Host, Server, Runner, manger I jot down in the rest room, including names. Most of the reports are long, but easy if you just answer each question.
Example: I arrived at this location at 1PM and observed two host at the podium. Mary smiled, made eye contact and said, "How many in your party?" I was told that I would be seated in 5 minutes. I waited one minute when the host, John escorted me over to a booth. He smiled and stated that Susan would be my server and be with me shortly, "Enjoy." At 1:10 PM Susan came over to us and asked if we wanted anything to drink, she offered a special beer that was on tap today. Our beer was served at 1:13PM. etc. etc. etc. Be specific on what the entrée looked like. The steak was cooked medium rare and warm. The steak was cooked to perfection tasty, juicy, and tender. etc. etc. etc.
The exact amount of time you will put in the questionnaire, not in the narrative. This has always worked for me and I have never had a return of the shop. I am sure many of the shoppers know how to write a report. If your new the first time is difficult. Timing is mostly what these shops are about.