You should check to see if your return air filters are clean and if they aren't, you should remove and clean them before re-installing them. Consideration also needs to be given to the environment as humid conditions may result in condensation dripping from the indoor unit (usually from the louvers).
Blocked drains can also cause water to drip from the unit and if you think this may be the case you should get your unit looked at by a professional. You will also find that the outdoor unit will drip water when using the air conditioner in heating mode which is completely normal from the outdoor unit coil condensation.
Drain plug kits are provided for the outdoor units in the box when new, so should be used at the time of installation if there is a chance of water dripping onto an area you would like to keep clear.