Repairing the seal on the dishwasher door eliminates the vast majority of dishwasher leaks. If the problem is a hose connection, the warranty on the dishwasher may require a call to a professional.
The next time a load of dishes is running, a place to start troubleshooting is right under the door. If drops appear there, it is time to check the gasket, which is the rubber seal that runs all the way around the perimeter of the dishwasher door. Clear cracks or other damage on the gasket means that a replacement is in order. Cleaning the gasket thoroughly with all-purpose home cleaner and a sponge is appropriate if no clear damage appears.
Finding the float switch in the owner's manual is the next step. Cleaning this with all-purpose home cleaner keeps the switch from sticking in the lower position, which can make the tub fill too high.
If the dishwasher door jiggles when it is closed and latched, adjusting the latch plate at the top center of the frame tightens the door, making a better seal. Even if there was no damage on the gasket, if the leak persists after cleaning it and adjusting the door, replacing the gasket comes next before calling a professional.