There are a bunch of different ways ...this is what i do ..
If the car is on gasoline- start it up and i spray "Engine store " like crazy into the carb till the engine starts to smoke alot and cough a little . I like to have the tires off the ground too. Then every once in awaile i just "bump the mtr over so the same spring isnt being compressed. I also ..which some here will disagree .. use "Sta-bil" in the gas. I have never had a single problem. I also keep a battery maintainer on all winter.
If this is Alcohol .. its a whole different animal ..
Hope this helps
Keith