Your POS System can tell you what has sold well in a department and it will tell you what has sold well with another product. This is all good stuff for upselling. The problem is that you are looking at is what was in your store, which is only a tiny subset of the products available plus it is only telling you what *WAS*. What you need to know is what is *NOW* and what will *BE*!
Here is a tip to help you to do this which you can do.
In Amazon Australia, you will find the best seller's list here.
Now pick a department say "Pet Supplies" and out will pop all the top sellers here
These are the top-selling items updated hourly, so it is current information.
Now go through the items and see which ones appeal to you. You will see the sales ranking. If you click on the items, you will see a lot of details, including what people think about these items.
I am sure it will give you a lot to think about them.
The best part about it is these are local products.
Now if you wanted to see what people in the US were buying, after all, they are not that different to Australian consumers, you can check the US website here
Be careful as although many think, that the US market is more advanced than ours. I am no so sure of this in my experience. It is an odd combination of being more advanced and more behind us plus it's a different market with different costs, benefits and requirements so be cautious about using it. Still because of its Winter/Summer being reversed there many of you will get many goods ideas of where the market is moving.