As backward as it seems, attempting 100% actually dings your score. There is an expectation that a good number of items won't be found/not carried/not an exact UPC match so 75-80% range was what I was told to aim for.
I would shop several areas for about 1-1 1/2 hrs. Just think of it as a scavenger hunt/video game: every item you can mark off drops off the list. If, after several visits, you're unable to locate certain items mark them as "not found/not carried". They'll come back on a future list. The main thing is to finish the list before week's end whether the items were marked "found" or not.
Dress comfortable/casual (no red & khaki) & wear comfortable shoes. I usually picked up a few items & had a drink with me.
Always stop by your store afterwards (depending on time of day) to download your current data. That way, should the system go down, you've got a partial list. Half a loaf is better than none.
It does get easier.