Take a copy of the photo page of your passport with you. If you could make it credit card size and laminated, all the better. In many places in the world it's a legal requirement to carry identification at all times. Having a copy on you lessens the chance your real passport could be stolen, copied or misplaced.
It's very easy to overpack. So make a pile of your proposed clothes, then be ruthless and take out any dulpicates. It's easier to wear layers. Shoes take up a lot of room, so plan to take multiple purpose shoes (e.g. evening shoes that could also be causal walking shoes).
Travel cards. Nowadays it is easy and safe to carry money in travel cards. These same travel cards can be used like EFTPOS overseas. (Do check with your bank about the features of their travel cards.)
Cash is always handy but never a grand plan to carry too much as it can attract unwanted attention. If you do plan to carry cash, be sure to hide it in multiple locations such as money belt, passport pouch etc. Just don't forget how much cash you have and where you put it! US dollars and Euros are the most widely accepted currencies abroad.
Credit cards are also a helpful way to pay for larger purchases; just let your bank know that you will be using the card overseas before you travel.
Along with all the usual items don't forget to take with you patience, tolerance and a sense of humour. It's part of travel that things will go wrong, there will be delays and the unexpected will arise. One of the joys of travel is "going with the flow" and enjoying the adventure. Things overseas are not as they are at home; that's part and parcel of exploring the world.
A sheet of bubble wrap tucked into your bag will be invaluable when you have that precious purchase you want to get home in one piece.
A collapsable, reusable bag can be handy. It can be used for: shopping, snacks, books, extra day clothes, picnic items, extra carry-on bag, washing and so on.
At the end of a hard day travelling, it's very relaxing to get into clothes that you find comfortable.
Use the first picture on your camera to take a picture of where someone could get in touch with you via email. Not a personal email, do protect your privacy, but where any honest person could get in touch with you. (If you travel with us we recommend you use our firstname.lastname@example.org.
To quickly identify your check-in luggage when there are hundreds of (black) bags rotating on the luggage caurosel, attach a recognisable tag. Make sure it's attached securely and your name can be read readily.
PS. When check-in staff give you that luggage identifier please put it somewhere safe. If your luggage should go missing the airlines will be able to trace and return it quickly using the identifier number.
Inner bags are smaller soft bags which you can use for keeping similar items together inside your large luggage. These bags stop things floating around and make getting dressed quick and easy. Keeping one for dirty washing is also useful.
Prearrange certain code words for you and your travelling companions to use when you are out and about. For example, use the word "mamafa"- the Tongan word for "too expensive", or talk about gardening when you want to leave. Speak out loud using New Zealand place names so it appears that you are speaking in a different language locals would not understand.