The agitator is the plastic piece in the middle of the basket that pushes the clothing down into the water. If your agitator is loose or broken, the clothing inside the washer basket will fail to circulate through the water properly. This can also lead to rattling inside the washer while the clothing is in the middle of a cycle.
The balance of the unit is important because it centers the washer while the clothing is spinning. Check the balance of the unit using a level. If the washer is unbalanced, use a screwdriver to loosen the screws holding the feet in place on the bottom of the unit. Place the level horizontally and vertically and adjust the feet until the washer is balanced.
The way you load clothing into the washer is an important part of the washing cycle. Make sure you do not overload the washer. If you overload the washer, the clothing will go to one side of the unit and knock the washer off balance. Evenly distribute the clothing for the unit before you start the cycle.
If your washer is not getting any power, it will not be able to turn on. Check the power cable going to the unit for any frays or breaks. Make sure that the power cable is plugged into the wall outlet in your home. If the unit is getting power, but the washer is not spinning, you have an internal problem that a professional must diagnose.