A vast majority of calls we attend for poor wash results are due to nothing more than blocked spray arms.
These are the arms that spin around inside your dishwasher with holes or jets along their length which not only spray water over your dishes, they also provide the propulsion to spin the arms too. Therefore, it is vitally important that these jets are not blocked or restricted.
Often bits of food debris, pips, bones, broken glass even, get caught in these arms as the debris is too large to fit through the jets. The only way to clear them is to remove the arms and poke the bits out of the jets, and shake the bits out of the larger central hole.
Consult you're instruction book should it not be clear how to remove the arms. Generally they are either clipped on or retained by a nut and some are trickier than others to remove-dont force anything as some of these parts break easily.
Once re fitted, ensure they can spin freely and not catching on anything and dont hang any fresheners or anything that may prevent them freely spinning. Of course, if you always ensure the filters are kept clean and are re-fitted correctly then large debris pieces will not be able to get into the arms in the first place.Please also have a look at the Self Help Section from this link before posting