Notes and Coins
In Bucharest you'll find 1, 5, 10, 50, 100 and 200 lei notes and 10 and 50 bani coins (100 bani = 1 RON).
ATMs and Banks
In Bucharest you won't have any difficulty finding cash machines and banks spread throughout the city.
How to Pay
The best way to save on commissions is to always pay by credit card, as then you'll be paying the current exchange rate and the maximum commission (which ranges depending on the card provider) tends to be around 1%.
Taking Money from Cash Machines
The commission that you are charged for taking money out in a foreign currency depends on your bank. You recommend that you check with your bank before you go so that you are not hit with any nasty surprises.
Exchanging Money in Bucharest
Another option is to exchange your currency for LEI when in Bucharest. There are plenty of banks and bureau de change offices where you can do this.
The exchange rate changes on a daily basis, but so that you have a vague idea, € 1 (US$ 1.10) = approximately 5 RON (US$ 1.10).