On a small service I do engine oil and filter. Check the air filter, brake pads, transmission shaft oil check that all levels are ok and that's pretty much it. On a larger service, 2 yr interval I extend what I do on small service to check or replace spark plugs if necessary, change brake and clutch fluid, clean brake calipers, wash brake and clutch system with methyl alcohol, replace air filter, fork oil, check rear suspension adjuster oil. Because I use high quality engine oil if I don't do much mileage, like this year, I will skip the service. As example, this year I'll be under 1,000 miles so I won't even look at it. next year I'm planning a trip to Italy so then I'll make a proper check and change the oils and fluids.