At home, an independent ATM may mean lower fees and convenient cash, but abroad they can mean trouble. If you don't need cash immediately, stick to ATMs inside or attached to banks to avoid currency conversion and other astronomical fees. Image from chucknado.
So how do you tell the difference between a good ATM and a bad one when you don't know the bank names or brands around you? Rick Steves explains how to tell the difference:
Most bank ATMs in Europe don't charge a usage fee, but stay away from "independent" ATMs, which have high fees and may try to trick users with "dynamic currency conversion." These ATMs (labelled with names such as Travelex, Euronet, Moneybox, Cardpoint, and Cashzone) are often found next to bank ATMs in the hope that travellers will be too confused to notice the difference.
If you're travelling to somewhere not in Europe, do a quick search before you go to find out the common names used in your destination for these types of ATMs. Beyond avoiding high fees, using the banks' ATMs also means you're less subject to scammers and can go inside the bank to ask for help if the ATM gives you any issues.
Tips on Using ATMs in Europe [Rick Steves]