Watch this video tutorial for troubleshooting dishwasher problems.
Check the following: are you over loading on detergent causing soapy residues? Have you stacked your dishes badly? Is the seal around the door old and worn? Do you have a dodgy pipe connection? Worst case scenerio is not good though, old machines corrode at the bottom and if this is your case then I guess it's time for a new one.
If you have no water, clearly the dishes are still going to be grubby. First check under the sink and make sure the hot water stop valve is fully open. If it is and there's still no hot water then now would be the time to call a repair man as this one needs the professionals.
A little water left in the tub is normal but if you're worried there are a couple of simple things to check: Is your drain hose damaged? Or are your drains blocked? If it's neither of these then you might need a new pump.
Bad loading is the most frequent cause of bad washing. Plates may be in the way of others stopping them getting any water so take a bit more care when stacking. If the problem continues you can try adding more detergent, but if that doesn't do the trick you might have low water pressure, or hard water. Call in a pro and they'll help.
You may be putting in too much of soap. Your dishwasher will only use the amount needed to clean the plates in it. Use less detergent for a couple of runs and see if that helps.
If you suspect the water is not heating properly hold a thermometer under the hot water tap for 2 mins. It needs to be a minimum of 140 F. If not turn up the dial on your hot water heater.
If it is making too much noise, then you may have some loose parts or you could just be stacking your plates badly. Once the machine is totally cold look around the inside for any hard object such as bones, or old knives and forks. Make sure the unit is on a level surface. If the noise is a thump then your inlet valve may be gone and unless you are trained then you may need t