The best thing, I think, is to go hang out in the store you want to restock in. For a day or two, when it restocks, don't buy anything. Instead, open a new window and check the prices of everything using the shop wiz... and I mean, run the shop wiz search like 10 times per item.
Then make yourself a list of what the store price is, and what the shop wiz price is.
Once you have done this for a day or so, you will have a good idea of which items you want to go after!
If you ever run across something that you can't remember or don't have on your list, just check it on the shop wiz. If you miss it, well, so be it... I guarantee if it was a good deal you missed, you'll remember it clearly next time