Stick to a budget.
Only buy what you need.
Buy off brand to save money
Start an argument with the cashier so you can get the manager involve and get free stuff.
Notice the cameras. Wear a jacket. Peel off barcodes while looking like you're examining the nutrition facts. Stuff **** in your pants. Walk out the door...
Hire somebody to carry your bags! Makes the whole shopping experience a lot more enjoyable.
Don't just buy stuff that's cheaper, check that it's not a smaller quantity, or lower quality.
Use a shopping cart. Preferably, one without a thumping, squeaky wheel.
Buy online as sometimes the delivery cost is cheaper than fuel/parking costs