A comon fault is small pieces of baked-on debris on crockery and glasses.
These come from broken down food particles and limescale left on the dishes before drying.
Use proper dishwasher salt - but above all be sure to use a good quality rinse aid - it helps the dishes to drain properly so that any food debris in the rinsing water runs away in sheets rather than remaining in droplet form.
Try to rinse off big lumps of food before loading the machine - consider a dishwasher cleaning tablet every few months or so - avoid the multi-tabs.
http://en.wikipedia.org/wiki/Dishwasher
Peccavi, June 2010
