Basic information surprisingly difficult to find.

So... I had an idea for a new invention to generate electricity. Got me a bicycle generator off the Internet. But then came the problem: all the schematics I could find about how to wire up a generator of this type neglected to show one basic thing: which end of the unit is the positive end, and which is the negative end? That kinda matters when connecting the wires. So I took it to my local bike shop to ask. The man behind the counter didn't know; said that with today's longer-lasting batteries, people who used to power their bicycle lights by pedaling just get battery powered ones now. Well, okay, but I'm not trying to power a bicycle light; I'm trying to build a new invention that uses a rotary action similar to pedaling. But now I'm stuck trying to figure out which end of the unit is which.

What about spinning up the generator(if not ready for the final mechanism to spin it, you could use a drill, perhaps?) and measuring voltage across the relevant points?

Digital or analog volt meter will tell you . Or if you have another electrical item that is reverse polarity protected, you can hook it up and see which wires make it run.