what make / model generator? you get more specific info if we know what you have.
the manuals are all available on line. get the one for your generator and see what it has to say.
alan f basically covered onan generators. i have one and change the oil, oil filter, and air filter at the start of each season. plus exercise it monthly.
one other point. if you have a gas fueled generator there are other things you should do such as adding a fuel stabilizer or running the generator dry so that you do not leave gas in the carburetor that can gum it up. again, this should be in the owners manual.
2015 cardinal model 3825fl
2015 dodge ram 3500 dually