On the subject of research, the more time you put in before the sales hit, the better your chances of getting what you want — what you really, really want. Signing up for alerts will do some of the legwork for you, but also take a look at when your favourite stores went on sale last year. For example, in 2019, the Boots sale started on Christmas Eve and Debenhams started before Christmas, too, while Marks & Spencer's 60-percent off sale began on Jan. 16.