Keep the instructions that came with your vacuum and refer to them periodically.
Keep hoses and attachments free from obstructions. Most vacuums that are discarded as nonfunctional often are only clogged somewhere in the unit. Learn where these likely places are from the manufacturer’s instructions.
Grip the handle, not the hose.
Keep brushes clean (for example, remove tangled hair) and replace them when worn. Typically, worn brushes are stiff, and they cause surface texture change on carpet.
Empty containers or replace bags when half full. (Just as you would not top off a car’s gas tank until it overflows, you would not want your vacuum bag to spill over.)
Look for rough edges or bent metal on your machine that can snag carpet.