Set a budget
Unless you're a millionaire, I wouldn't skip this part.
I set a budget for myself. Most trips I set a $2000 budget. That's typically a 10-20 day trip depending on where i'm going.
I have an excel spreadsheet, or use google docs (thank you Katie) so you don't lose all your documents when your computer decides to go live a life of it's own. Not talking from experience or anything.
SPREADSHEET EXAMPLE COMING SOON
I recommend having a credit card when traveling for a couple reasons. 1. 0% foreign transaction fees (with some cards) 2. Why not earn points while you're traveling to use towards your next trip!
*You need a PIN with a credit card in most countries, this isn't something we use a lot in the states, but call your bank and set up a PIN, you will thank me later.
In the event your things get stolen, your bag slips out of your hand and into the ocean, or a giraffe eats your shit I would have a back up plan. Although your back up plan is probably chillin' in the bottom of the ocean now.
CASH. Don't rely on your travel credit card for everything, yes most countries accept major credit cards, but there are still a ton of places that do not. Especially taxis (not a place). side note on taxis: always ask for the meter, if they tell you no get the f+ck out of the car.
DEBIT CARD. I don't always bring my debit card, but if you're bringing a small amount of cash I would bring this as a backup in case you need to pull out more cash. Just be aware of the bank fees you will incur. They are fun.