A clothes washer keeps draining well for a long time, and most of what keeps it that way is small upkeep you can do yourself. The drain side gets the least attention. It is also where slow drains and standing water usually start.
Find the filter and know where it sits
Front-load washers usually have a filter behind a small panel at the bottom front, reached with the lower access door open. Top-load models often keep the filter inside the drain pump housing, which is reached from the back or from below depending on the model. Read the manual's section on the drain filter before you open anything, and keep a shallow pan and a towel underneath.
Clean the filter on a schedule you can keep
Empty the filter when you notice slow drainage, a gurgling sound at the end of a cycle, or lint and small objects collecting in the trap. A household that runs the washer every day will need to check more often than a household that runs it now and then. Rinse the filter, remove any buttons or coins, and reseat it firmly so the seal is clean.
Check the hoses and the standpipe
Look at the drain hose for kinks and cracks. Confirm the hose is held at the correct height and does not sit down in the drain basin, which can siphon water back into the drum. Make sure the standpipe or utility sink can carry the discharge. Wipe the fill hose connections and look for drips at the valves.
Keep the record
Write down when you cleaned the filter, what you found, and any service visit. That record shows how the washer is aging and gives a repair person a clear history. Then compare the washer's expected life on the clothes washer page so you can plan the next decision in good time.