Normal ATM debit Card to get cash from ATMs, Maestro Cirrus works in most places, Plus is another brand just make sure you check the ATM before popping your card in to make usre it accepts your card type.
Credit Card for emergencies. If going to iffy places watch it like a hawk when getting it swiped you don't want it cloned.
Don't bother with travellers cheques if you go to exotic places they will just laugh at you even in the banks.
It all depends where you go, if you go to a country where people earn $300 a month then just take $500 in cash and live on that for a month exchange it as needed and hide the rest well.
Check your overseas transaction fees for each method you are thinking of using.
Biggest thing is keep all numbers for the banks in case of card loss in several places I usually email my yahoo address all details in case I really get taken for ride. Just account numbers etc no PINs.