If you're gf and live near a Wegmans, you (1) are so lucky! and (2) probably already know that they label gf store brand items with a big ol' "G" on the front.
They also offer a printable PDF of all store brand gf items as well as a cross-referenced list of items that are gf AND lactose-free, should you need to steer clear of both. (The lists are updated weekly, so make sure you use the latest version.) If you see something in the store that looks like it should be labeled gf but isn't, you can always call or email them with your query. I did that a few times when I was new to the diet and found them unfailingly helpful and patient. They also offer "Menu Magazine", a quarterly recipe collection (both in-store and online), full of delicious recipes with the gf options clearly marked.
While I have many gf grocery shopping options here in NYC, I've been missing Wegmans lately; if you live near one, you totally understand why! The stores are amazing and the company's labeling policy serves the gf community very well. In addition to the store brand they carry products from major gf labels and I've also found them amenable to suggestions about new products to carry.
Don't have a Wegmans in your area? They're expanding - check out their list of potential new sites!