Make a point of...
a) Always using the best Rinse Aid you can find. Its job is to reduce the surface tension in the rinse water to let it drain off before the drying cycle. If droplets are left on the dishes the drying process bakes on hard any grit left in the water.
b) Try as often as you can to rinse off food debris before you load the washer. The crud that sticks to your crocks can only come from the dishes you put into the machine - it's usually got tiny flecks of tomato in it when it happens to our machine, or egg or weetabix or all three!
c) Use dishwasher salt and top up when it runs out especially in hard water areas
d) Clean the filters and spray arms - the little holes in mine get blocked with paper debris from jam pot lables
a) and b) are the most important.
Good luck...
Peccavi
April 2009