i am to visit usa and enquire which plastic to use if i want to get dollars ,visa card/debit card. if visa are all treated same ie charges if any. is there any tips i should no! thanks for any help.
You should use a debit card, not a credit card. With the latter you will incur interest as well as extra charges for cash.
The best debit card is a Nationwide one, which won't load the exchange rate you get. Others will - though not by as much as the rate used for changing cash.
Use bank ATMs - not those in gas stations or convenience stores which may add their own charge.