John Deere makes a very useful document, called a maintenance reminder sheet, for many of its products. This one-page PDF file is a good reference for maintaining your mower. It contains part numbers and locations for commonly-replaced parts (such as oil filters, fuel filters, spark plugs, and blades) as well as service recommendations, compatible accessories, and links to online JD resources. At the bottom it will also typically list the part number for the JD maintenance kit for that mower.
You can find links to maintenance reminder sheets for many John Deere mowers on this site's John Deere manuals page (below the manuals).