If your computer mouse is erratic, try cleaning the rollers:

Turn the mouse upside down. If it has a little ball, open the retainer by turning the plate with your fingernails. Most have arrows molded into the plastic to show the direction of rotation to remove the plate.

Carefully remove the ball and set both it and the plate aside, you will need them later.

You will see two roller wheels and/or two roller bars inside the hole.

They probably have a coating of rubber built up in the center of each bar and wheel, gently scrape the rubber buildup off the center of each with your fingernail being careful not to bend or break anything. A little practice will teach you how to simultaneously scrape and turn the wheel or bar while scraping it. Don’t use anything harder than your fingernail or you will score the plastic or metal and they will get the buildup much faster and more often.

It helps if you also wipe the ball against a piece of cloth to remove any excess rubber buildup on it.

Drop the ball back in and reinstall the retainer plate.

You now have the equivalent of a brand new mouse!