Make sure you have valid passports for every member in your family or travel party. This includes pet passports if you're travelling with your dog. There's nothing worse than turning up at the airport then getting turned away because your passport is not up to date.
Plan your outfits
This tip is very helpful so you don't overpack or underpack. When you already know your itinerary, it would be easier for you to determine what the appropriate attire would be. Make sure to bring at least one extra outfit just in case something happens along your travels (but hopefully not).
Know how to get from one place to another
If you aren't booking a private ride, then it's best to know in advance what train stations or public transportation vehicles you should take in the place you're going to. In this way, you won't be so frazzled finding your way and you would easily get to your destinations with less hassle.
Learn the basics in their language
Not all countries are English-speaking and some don't even have enough knowledge of basic English words. While there is nothing wrong with it and that is perfectly normal in other places, you as a tourist should be able to know how to communicate with the locals. Know how to ask where the restroom is, where the train is, how to get a cab, etc. The basic phrases you should know should be able to help you navigate your way through the city. Learning a few greetings would be great, too!
Have enough pocket money
Depending on your trip and the places you will go to, determine how much pocket money you will bring. Most of the time, pocket money is used for shopping, souvenirs, entrance fees, and emergencies. Having pocket money is always going to be a smart move because you will have backup during the times that you won't be able to expect unnecessary expenses.