How do you tune up push mower?

At the end of the season or at the start of the season, use a turkey baster and suck all of the old gas out of the tank. Place a plastic bag over where the gas goes in and tighten the bag with the gas cap. Drain oil by either tipping the mower over (with the plastic bag over the cap) or locating the drain plug underneath the mower by the blade. It is best to take the blade off and sharpen it if you are going to drain the oil. Replace spark plug if it is old and you think the mower isn't getting enough spark. Locate air filter and find replacement filter for it. These are some of the basics that anyone can do, getting the carb cleaned is the next step if your mower is still not running at a top. This takes a little bit more skill and time.