The traditional tuneup is a thing of the past. Today’s cars should be maintained by what your owner’s manual says.
As per above post, the items that are addressed in a minor tuneup are spark plugs, air filter, oil and oil filter, fuel filter, and at high milegae cleaning out and inspecting the fuel injectors.
The frequency of all these items differs by make of car, and you should follow the maintenace manual. Platinum plugs are good for 60,000 miles, while regular plugs are 25,000 miles at best.
Other items necessary, but not normally called a tuneup, are changing transmission fluid and filter every 35,000- 40,000 miles, flushing the cooling system every 4 years or 50,000 miles, and replacing the timing belt (if the car has one) every 60,000 miles. These last 3 items can result in very expensive repairs if not performed on time!!