Read the specifications for the printer - usually they're printed on the box and will list Mac OS X (and the specific versions) if it's supported - or ask the dealer or printer manufacturer. They should be able to tell you if the printer is compatible with your Mac. Apple also has a list of printers for which they include drivers in Mac OS X here:
though that list may not be completely current nor all-inclusive of every printer for which there are drivers.
If there's a particular model of printer that you're considering, you can also do a web search or post the printer model here and ask for opinions.
Message was edited by: varjak paw