If you have an idea of what you want before the sale starts and know how much the standard price is you can still be lucky and get a good deal. You just have to be careful not to get sucked in to a non deal.

For example, I was looking out for an Apple Watch. There is a good sale on them but they only have a limited set of body and strap combinations. I don’t want any of the straps on offer so it negates almost all of the discount as I’d be paying £50 for a strap that I wouldn’t use.