It Can't Carry the Load
One of the most common reasons for a dishwasher to break down or leak is improper loading of the machine. Make sure when loading the machine not to overfill it. Leave space between your dishes, and be certain that there are no pots, pans or dishes obstructing the spray arms. This can lead to the water being unable to spray in its intended directions, thus leaving it no other choice but to leak out the front and sides. Spend a few moments glancing at proper loading techniques for the dishwasher and you can avoid this unfortunate result.
The Soap is the Culprit
Another reason your dishwasher may cease to work properly is the use of improper soaps. Only use those detergents that are specifically designed for dishwasher use. A common and regrettable mistake is to try and use sink-top dishwashing liquids like Joy or Dawn in place of machine dishwashing detergent. This can lead to not only a leak, but an outright flood, as the sudsing properties of these sink-top liquids is not meant for the forceful spray of the dishwasher. Along the same lines, make sure your rinse aid (like Jet Dry) is within its proper dispenser and has not spilled. This spilled rinse aid can start to foam and cause the same effect as the sink-top dishwashing liquids.
The Door is Letting Water out
Check the door seal on your dishwasher and make sure it is sealing properly. If it is not, consider cleaning it. This is sometimes all it takes for it to regain its sealing properties. If it needs replacing, consult your owner's manual for instructions on obtaining replacement parts. Make sure nothing is blocking your detergent dispenser when you shut the door. This could be again a symptom of improper loading or overfilling. This could lead to a backup of the detergent, giving you the same leakage problems evident with the use of incorrect soaps. Also take the time to make sure your dishwasher is level, and is sitting on all fours. An off balance dishwasher can easily lead to leaks from the sides or the front.
The Spray Arms and the Motor
Sometimes it is the spray arms that break down. If this happens, make sure that you haven't loaded the dishwasher in such a way as to block the spray arms from their full range of motion. If this isn't the case, consider that your dishwasher may have alternating spray arms. If the motor won't start, check the circuit breakers to ensure that the breaker hasn't tripped. Make sure the door latch is securing properly, because many dishwashers won't function unless this is the case. Check and make sure the delay start mechanism isn't on.