Make a list of your requirements:
First and the foremost thing you should do is to decide what type of sea kayak you need. It depends on the nature of your trip as day trip, international expedition, touring, racing and surfing require different types of kayaks. Make up your mind as to what type of sea boating you want to do and then purchase a kayak which suits you.
Read buyers guide:
There are many guides available in the market for this purpose which can really help you in choosing the perfect boat. Moreover, you should browse the internet and visit the websites that offer assistance in such things. You will need a regular touring kayak if you are new to water sports and just want to have some fun on weekends. However, if you want to pursue boating as a professional then it is better to purchase an expedition-fitted kayak, packable kayak, surfing or racing kayak.
You may seek help from experienced persons. For that, visit your nearest launch site, examine all types of kayaks and talk to the owners about their boats. Believe me, no one else can guide your better than someone that has experience using a kayak.
Try out a kayak:
You should request the owner of the boat to allow you for a test ride. However, make sure that you are trained to handle any situation. Moreover, dress up properly for the water as anything can happen if you are new to this sport.
Visit the market:
After getting a clear idea about the kayaks, you should visit the market and find a kayak dealer. Ask the dealer to show you some of the best boats. Check the material, durability, design, size and safety. If you are satisfied with the boat, ask the dealer for a test ride and make a deal after a proper check up.