The first thing to consider is the country itself, you can pay for things with credit cards in most first world countries, but developing countries are not quite as simple- usually major hotels will take your credit card, but you may be out of luck in other places like restaurants, etc… If you do have a large amount of cash, you can usually leave it a safe in your hotel, either in your room or in the lobby.
The simplest and most convenient option that I use is to bring cash and change it at the airport when you arrive. The main problem with this is that the rates are not always good, and you also usually have to pay a service fee. I do recommend this to get some small amount of local currency just to get you started- for lunch, taxis etc… When you have to change a relatively large amount of money however, you really have to look around for the best rate. On a recent trip to Scotland for example,Â I changed 500 USD at the airport for 242 pounds, then a few days later exchanged the same amount again in a store for 252 pounds- that’s a 10 pound or 20 dollar difference- which is the price of a nice lunch.
Another option if you are a person who likes to carry cash, is to take money out directly from a bank (ATM) machine. This is possible in many places by checking the back of your debit card to make sure that one of the networks is listed on your card and also on the machine you are withdrawing money from (examples of these are cirrus or plus)- your bank will sometimes charge a fee for this, but the exchange rate is usually pretty good. DO watch out for suspicious people around ATM machines- I have had my bank account accessed in the UK after I had used a particular machine, I had not noticed anything unusual at the time but a few days later I checked my account and had $2,000 withdrawn over the period of five hours. Somehow they managed to copy my card and pin number from a particular machine.
A third option is to pay for everything on your credit card, you will not need to pay a separate fee, however, the exchange rate they give will include a small percentage exchange (usually 2-3%)- this is probably around the same rate as you would get from your bank?
I usually tend to use a combination of the above ideas- varying the amount of cash I carry depending on the country I’m visiting- the less I think I will be able to use my credit card, the more cash I will carry. But I always carry some cash because you never know when you will need it.