I do a LOT of business with Staples for office supplies. If you are on an email list, you can check you recent emails for advertised specials that require a promo code, then copy & paste it during checkout online. Yes, there are often caveats, like you cannot be purchasing an item alREADY on sale, OR you have to meet the threshold $ for your order, and those things will kick out your promo code.
It is STILL worth checking bc I have gotten many items for a fraction of the cost, ESPECIALLY on a
"Deal of the Day." I bought a $400.00 pair of hunt boots (DH told me to buy for Christmas, 2017, then tell him from who and how $much) for $89.00, Deal of The Day on Horseloverz. I have bought office supply items for a fraction of the cost.
Sometimes, you get a break buying online to pick up at the store instead of shipping, so look for those, too.
MOST IMPORTANTLY, get on the email list for your favorite places to buy.
EVERYTHING is online today.
ALSO, it doesn't hurt to have a coupon On your phone AND printed.
Guy in front of me at Rural King couldn't use his coupon bc it Wasn't printed, just on his phone. He missed out on a 1/2 price sale a few weeks ago.
There are still stores that require you to use their promotion hard copy and fill that out AND snail mail it in.
Menards (MidWest hardware chain) does this. SIL complains about having to do this, BUT, they mail you back a card with your discount and it doesn't expire.
SOMEtimes you will get a rebate card, looks like a credit card, AND it HAS an expiration date.
This is a learned skill, But I think it's worth it.