If I need to withdraw cash at the ATM, what is the best practice to minimize fees? In the USA I bank with Bank of America.
Bank of America is part of the so called Global ATM alliance. According to Bank of America's FAQ (see "Using your ATM card or debit card at an international ATM" and then "What is the Global ATM Alliance?):
Use your Bank of America ATM or debit card within the Global ATM Alliance to avoid the non-Bank of America usage fee for each withdrawal, transfer or balance inquiry, as well as the ATM operator access fee. An international transaction fee of 3% will apply when converting your currency.
In France, BNP Paribas is part of the alliance and you can use your Bank of America card at their ATMs to minimize your cost.
Note that BNP Paribas doesn't charge any fees for using their ATM (according to TransferWise), so the only fee you'll pay is the relative transaction fee. There seems to be no minimal transaction fee from Bank of America's fee schedule (it's hard to link to it, you have to select Bank of America Core Checking and enter a ZIP code, then go to ATM fees and View more important information), so it shouldn't matter whether you withdraw a large amount once or many smaller amounts (but it's better to check after your first withdrawal just to be sure).
However, when you try to withdraw money from a BNP Paribas ATM, they might offer you to do a conversion for you. In this case they will offer you two options: a.) to withdraw the Euro amount in which case the currency conversion will be handled by your bank, or b.) to withdraw a Dollar amount in which case they handle the conversion. Of course, they don't do this for free and I've never been anywhere where it would have been better to use the conversion offered by the ATM. Bank of America agrees on that:
Bank of America will assess an international transaction fee of 3% of the converted US dollar amount. Foreign ATM operators may offer to do your currency conversion for you, but they may charge a higher fee for conversion. To insure that your currency conversion does not incur a fee higher than 3%, you may refuse the ATM operator's offer to convert the amount of the transaction.
For next time though you could consider getting a bank account with debit card where you even don't pay (or are reimbursed for) currency transactions. Such accounts are offered for example by Charles Schwab or Capital One 360.
Further to @martin.koeberl's answer, from the Bank of America's website, there might also be local fees to pay and you may not be able to find a BNP Paribas. When I worked in France but had a UK bank account, the simplest way to minimise ATM fees was to minimise the use of the ATM. When I did go to the ATM, I withdrew a significant amount of cash. This amount will of course vary according to your needs but I took out the equivalent of a week's spend each time. This meant that by and large I went to the ATM four times a month and so only paid four lots of fees.