As above, get yourself a Visa debit card and where possible pay with it, like a credit card. That way Visa cop all the fees.
If you need to get cash out, then get a few days worth at a time as from memory, it costs about $6.00 in transaction fees for a withdrawal O/S.
Travel Cards are a good option if you are going O/S in say 6 months time and you think the exchange rate will be significantly worse by then as a travel card will lock the exchange rate in now. It also means you can't access your cash for that period of time though so don't lock away too much. The bank do, however, charge a commission.
If you are changing over cash, do it at a bank before you leave. Don't do it at a travelex or at the airport unless you absolutely have too as they smash you for the priviledge.