Mix and match separates are the best way to create more outfits when travelling. Stick to a basic colour scheme to increase available combinations.
I consider the hair straightener one of God’s gifts to the curly-haired, and will certainly not travel without it. Make sure you have one that is dual voltage if you are travelling to USA.
When travelling to tropical destinations or on a cruise I take a couple of bolero type cardigans, to cope with occasional too-cool airconditioning.
Always assuming I am going to be buying some clothes during my travels, some of the clothes I take are items that I am on the verge of either giving to the Op Shop or throwing out. This way, I can replace said items and not add any more weight to my luggage, leaving space for other souvenirs.
That’s another important thing to consider: excess baggage. If you have an allowance of 23 kg. make sure you leave for your holiday with only 15 kg., to allow for purchases if you know you like shopping.
I used to pack everything I might ever need, but am slowly learning that if I forget something, I can buy it at the destination. Perhaps it’s a throwback to travelling when young and impoverished?