1. Dress comfortably: If there will be anything stopping you from continuing a good well-deserved shopping spree, it would have to be comfort. For once just forget about dressing up and keep casual and comfortable yet stylishly. I personally also recommend wearing particular items of clothing which are easily to put on and take off in case you want to go ahead and try on other items as this allows you not to waste any time in the process of shopping as opposed to wearing a complicated messy outfit.
2. Grab and Go: Just imagine how crazy the crowds might be at large sales events especially Boxing Day. They will pull and grab at just about anything and you wouldn't want to be caught in the middle of it all. My suggestion is to grab as much as you want (that fits you and all) at the first go so that you can rush to the changerooms to try stuff on because chances are that the queus with be very long and if you take your time, the items which you want might not be available for very long either. To Grab and Go really is quite a win-win situation for a big sale event.
3. Be in good company: The last thing you want is to go with a massive group of friends. I usually find that taking one good honest friend with you is the safest option as you will be shown a variety of options in terms of clothing and because it is so hectic, the last thing you would want is to have to wait up for others. Time is precious and when you come home with only one item after a complete day of shopping, you will realise this. No children and no boys! Good company will make your sales shopping more enjoyable and less time wasting.
4. Be polite: You don't want to be remembered as the crazy woman who pushed and shoved everyone out of the way during sales time. Instead, act with grace but be firm on what you want. Remember that it is just a sale and it isn't the end of the world. If you find something you want which isn't available, don't ponder over it for too long and move on. Chances are something else would've caught your eye and you won't end up being the scary customer which no one wants to help out.
5. Have fun: Sales don't happen everyday so enjoy the rush and the moment while it's there. By the time you get home, you will be so relieved and just ready to fall asleep so enjoy the feeling of frenzy while it's there. You will be so pleased with your purchases if you have a positive attitude and remember that you did get it on sale so being picky would be one of the last things you can be. Beggars can't be choosers so enjoy it. 
xx Lisa