Credit cards are the best nowadays. Just be careful in some countries where they pass on your numbers to someone in another country and your cards get to be used. These days, most cards have pins so there is no danger of that.
We haven't used traveller's cheques for over 17 years now. You can hardly find banks in some countries that will do the transaction.
Bank cards are also useful as you can take money from ATM's. They are all over many countries now. Just be aware of the fees charged by your banks and the local ATMs. In some countries, they limit the cash you can withdraw from the ATM's to a ridiculous level that in these cases, we bring cash instead. Thankfully, there are not too many of these countries with so many restrictions.
We make it a rule to always bring some cash with us. Not much but enough so in case you can't find an ATM or not have the time to go to one, you have a bit to get you through.