Change oil every 2500 – 3000 miles or every 6 months whichever comes first.
Change Automatic transmission fluid every 12,000 miles or once a year whichever comes first unless the fluid has not been changed and is burning.

Otherwise it is best to leave the transmission fluid alone especially with a high mileage vehicle. Fresh transmission fluid contains detergents that can eat away the clutch inside the transmission if they are already burning so it is important to make sure not to change burnt transmission fluid unless you want to replace your whole transmission.

There is a difference between burnt transmission fluid and transmission fluid that is just dirty.
Check the brake shoes and lines once a year or every 6 months if you do a lot of city driving or stop and go driving.
Check the tires periodically to make sure there is enough thread and there are no bubbles in the tires.

Have the front end checked including the axles and boots every time you go for an oil change. By the front end I am talking about all the linkages and ball joints, the bushings and rack and pinion steering as well as the wheel alignments.

Checking your headlamp bulb periodically as a bulb can be out without you even knowing it as well as the tail light bulbs.
Make sure your fluid levels are always full #MOST IMPORTANT# in the engine.
To keep the body paint fresh and protected it is always a good idea to have your car waxed every couple of years.

Check the windshield wiper blades periodically.
Put at least a 91-octane fuel in your gas tank, as there is a difference in the way your engine will run if you avoid the lower octane gasoline.
It is always a good idea to put a can of fuel injection cleaner in the gas tank once a year, as it will clean the injectors, as well as the carburetor if you are equipped with a carburetor.

Tune your engine up once a year or every 12,000 miles whichever comes first. During the tune up have the mechanic check out the belts, hoses, wires, filters and give it an overall inspection #VERY IMPORTANT# Use a trustworthy mechanic who specializes in the vehicle you have; for example do not use a mechanic who mainly works on domestic cars, if you have a foreign car.

Also, a lot of mechanics will try to sell you parts that are not necessarily needed, so make sure you are not being taken for a ride so to speak by your mechanic. There are some honest mechanics out there, but like everything else there are some very dishonest ones as they are a dime a dozen.