A little disclaimer, Some of my tips may seem tacky, but we are going for optimizing our money and loyalty rewards.
Open your gifts / Check Gift Receipts
See what you received for Christmas first, maybe some people gave you a gift receipt. If you need to exchange or return something, this would be the day to do it so that you can use the store credit card purchase something else or exchange for the right size.
Build a Running List
Keep a list of items that you will need to buy soon or at some point in time, so that you know what prices to monitor. This way, when the right offer comes around, you can buy it or buy it ahead of time to stock up., which leads nicely into my next point.
Know Your Sale Prices Throughout the Year
There are continually sales throughout the year, where Boxing Day may not necessarily be the only day that we see the best deals. For example, if I had a item that I wanted to buy and I was not in a hurry, I would track it for a few months to see what sales are available. If I noticed 25% off every 3 months, but suddenly it is 50% off on Boxing Day, then I would be more inclined to buy it. However, if the reverse was true and there are frequently 50% sales, and it is only 30% on Boxing Day, then I know it was not a good deal.
Have Your Credit Cards and Loyalty Cards Ready
If you know you are making a purchase at a specific store, know which loyalty card and credit card give you the most bonus rewards for that purchase.
Alternatively, you may also find better prices online. So be sure to use shopping portals to earn even more bonus points.
Some stores even offer you a price match. Basically, if you find a lower price at another store, you can show it to the cashier, who will at least match you the same price. Some stores offer an additional discount. Beware that sometimes, physical stores may not necessarily match an online only price.
Merry Christmas everyone and Happy Shopping tomorrow if you choose to go out!