I've been working DEEP discounts at Lowe's recently.
First, I score discounted gift cards from gift card resellers. AND I use a click through portal for additional discounts.
Then, I order everything online after clicking through a cash back portal.
Then, with Lowe's 20 min guarantee, your order is ready within 20 mins of placing it or they drop a $20 gift card on you (store policy varies). I don't really put up a big stink if they are a few minutes over and are working towards getting everything together (e.g. my last order they guy was on the way with one of the items and it was an extra minute or two). But if I stand around for 10 mins, "is the manager around?"
Doing this nets you a 17.2% discount, plus a gift card if they don't have it together at the store plus you can stack coupons on top of that. Cha-ching.
In store antics include hauling in every competitor coupon you can find (harbor freight, local hardware stores etc) and having Lowe's match the offer. My in laws are also have military ID's, so they meet us at the store if we don't have a 10% off coupon for big purchases (another 10% off).
Some people also buy extra things online (get 6.5%) then exchange it for merchandise credit. I don't personally go out of my way to do this...use your own moral compass.
Then, the price match guarantee, they'll beat the competitor's price by 10%. We're looking for an upright freezer, so we look at competitor's ads (probably have to look until the 4th or labor day).
Also, Michael's had Lowe's $50 gift cards for $40. Got about $3500 worth.