Rent locally and explore your nearby waterways. You can be one of those kayakers serenely paddling past the chic waterfront eatery in your own town. See: http://www.bask.org/outfit.htm for a list of outfitters.
Step2
Rent while out of town. You can find novice-friendly conditions in Hawaii, Baja, Canada, Alaska, and Italy (http://www.seakayakitaly.it) and more. See: http://www.bask.org/outfit.htm , Wavelength http://www.wavelengthmagazine.com/ and Sea Kayaker Magazine http://www.seakayakermag.com/ for a list of outfitters.
Step3
When you complete a beginner's course in sea kayaking have the instructor give you a certificate of completion. Bring the certificate to show to kayak rental companies to authenticate your level of experience. Some won't rent to folks who have never taken a course.
Step4
Choose a double or a single kayak. Doubles offer more stability and speed, but require cooperation between the paddlers. Some folks call them 'divorce kayaks.' They often make sense when one paddler is more experienced or stronger than the other. In a double no one is left behind. Singles give a paddler a sense of independence and mastery. However, a weak paddler in a single can put an entire group at risk. Consult with the outfitter when choosing your kayak and take their advice.
Step5
Inspect the rental equipment. Check to be sure that: the rudder (if equipped with one) works, the seat fits you comfortably and is sound, the foot pegs are placed properly for your leg length, the kayak has no obvious leaks. Be sure the spray skirt is not torn. Be sure there are float bags in the hatches. Each kayak should have a bilge pump and a paddle float for re-entering the kayak. (You learn how to use these in your class.)
Step6
Sit in the kayak to be sure it fits. A good outfitter will adjust the seat and foot pegs of your kayak so it fits you. If your kayak seems too big or small tell the outfitter. Rental fleets often include smaller kayaks for smaller people and larger kayaks for larger people.
Step7
Allow enough time for the trip and bring the kayak back on time. A late kayak is not only inconvenient for the outfitter, but in may signal the start of a rescue operation.
Step8
When on a self-guided trip follow the route and advice provided by the outfitter. If needed bring a map.
Step9
Be prepared!
Step10
Dress for the water temperature in clothes designed to keep you warm in the water. Outfitters who rent on cold water usually include the cost of a wetsuit rental in with the cost of the kayak. Choose neoprene (it comes in many different weights and styles), and waterproof thermal fleece. Wear polypropylene and other synthetics. Avoid cotton. If you get hot just wet yourself to get cool. It's much harder to warm up when cold than cool down when warm. When you paddle in warm water in a warm climate protect yourself from the sun with a wide-brimmed hat and long-sleeved shirt.
Tips & Warnings
When you rent a sea kayak for the first time, rent from an outfitter who provides a free introductory course in sea kayaking, or combines a class with a trip.
Pack a change of dry clothes and some money in a dry bag supplied by the outfitter. But don't bring anything you can't afford to loose.
Wear a hat and sunglasses. Use sunscreen. Glare from the water can be quite bright.
Bring plenty of water and food, even for a short trip.
Don't go out if bad weather is expected.
Some programs are available for people who want to sea kayak and have physical disabilities. Visit Environmental Traveling Companions at http://www.etctrips.org.
Sea kayaking is a sport that requires strength and endurance. Be honest with yourself about your physical condition. If you are not physically active and are not sure that you're in good shape, check with your doctor before you rent.