Where are you planning on taking the test? It varies from state to state. For instance where I live in Idaho if you've never taken and passed a driver's ed course then you'll have to take a road test (or parking lot test, whatever it is) as well as the written.
If you are going to get ride a motorcycle you'll first need a driver's license. You can take a written test to get a day pass, which basically means you are OK to ride a motorcycle during daylight hours, and (correct me if I'm wrong) you cannot operate them on the freeways.
To get your actual motorcycle endorsement in Idaho you'll have to run a rather stupid motorcycle course, stupid in the sense that it is pretty easy to fail if you are on a bigger, less nimble bike. I'd cringe if I saw anybody trying to navigate it on a Honda Goldwing. But that is just in Idaho, the tests and endorsements aren't mandated on a federal (countrywide) level and are up to the state to decide how to go about it. In my state it is notoriously easy to fail the written tests do to all the dumb arbitrary questions they ask (most don't pertain to the actual operation and laws of the state, trust me it is very very dumb and you'll almost have to get Idaho driver's handbook to study beforehand)
At any rate, phone ahead to the DMV of whichever state you plan on getting licensed in, I am sure they can fill you in on everything you need to do. Also I'm sure they have available all the literature you'll need to study before taking any written tests.