First thing you need to do is find out if your washing machine actually has a lint filter. My HE machine didn't, my new machine does, so check your handbook to find out if your machine has a lint filter.
If your washing machine is a top loader it should have a lint filter in the agitator. Pull out the top of the agitator and it should have some kind of little bag or basket attached to it.
Gently take it off and give it a good clean. You may need to empty the lint out of it first. Then rinse it under hot water. If you use fabric softener then you will also need to soak it for a few minutes in white vinegar. Fabric softeners leave a film over the mesh that actually stops the water from getting through. You need to get rid of this build up.
Front loaders have different lint filters - check your handbook to find out where it is and how to get to it.
If you empty and rinse the lint filter after every wash you'll stop those black flakes of gunk that sometimes appear on your washing - that's the old muck out of the lint filter flowing back up into the bowl. Yuk!
While the lint filter is soaking, get a cloth and a bucket of warm water and add a splash of vinegar (about 1 cup). Use this to wipe around the top of the bowl, under the lid, over the outside of the cabinet etc. Don't forget the inside of the agitator and the fabric softener dispenser. If it's particularly grungy, sprinkle with bi-carb and use this as a scouring powder. Just watch your fingers - the edges of all those ridges and rims can be sharp (guess how I know!).
Put the lint filter back together and replace the top of the agitator. Then run your washing machine through a full cycle on the longest and hottest wash cycle (this is the only time I use a hot wash) and add a full 2 litre bottle of vinegar to it. Don't add any clothes or other detergents; let the vinegar work its magic. The vinegar will remove the scum and gunk and any hard-water build up in the bowl and hoses.
Wipe over the outside of the machine with a damp cloth and dry.
You washing machine will sparkle inside and out. Do this on a regular basis and you'll extend the life of your machine and save on costly maintenance calls.
My handbook suggests every 100 washes, for me that's about every two months because of the amount of washing I do. For my mother it's every six months or so as she only does two loads a week. If your family is larger you may need to do this more often. It may seem like a tedious chore but it is worth taking care of this most useful household appliance.
Think about what you'd do if you couldn't use your washing machine for a week - hand-washing, paying for the laundromat -and you'll see the benefit quickly.