Oh I like that petpage. I was always wondering what restocked in which shop.
I have been looking for one that is complete with each thing that stock in each shop, but none of them are completely finished.

Sniping, you can either snipe the auctions(be quick and buy an item for cheap then resell for more).

You can restock in the main shop then resell those items.

You could also snipe user shops using the shop wiz, but that requires quite a bit of luck :p