A clean sewing machine makes a bigger difference than you'd think. Here's the most effective method, plus the mistakes most people make.
Always unplug the sewing machine before cleaning to prevent electric shock.
Remove the needle, bobbin case, and any other removable parts according to your manual.
Use a small soft brush to remove lint from the bobbin area, feed dogs, and around the needle plate.
Lightly blow out lint with low-pressure compressed air. Never blow lint deeper into the machine -- always blow outward.
Apply a few drops of sewing machine oil to the moving parts indicated in your manual. Wipe off excess.