Take a taxi and ask the driver to take you to the town center of Akritochori, or if you have rented a car, it is about an hour from Kalamata. Road directions from kalamata can be found [http://www.mapquest.com/#b4ee134fb2f98780c1a70f17 here.
Small passenger boats often moor at loutsa beach. Do not take these are they are slow, unreliable and expensive.
The best option if you want to get in by boat is to rent a boat in a nearby town and drive it to loutsa.
Many private airstrips operate in surrounding areas, but most have unpaved runways and are only used by the owner. Kalamata airport is an hour away.