What is the use of the kayak going to be? Touring, recreational, white water or ocean . Each of these takes a totally different kayak. Length of the unit is important also.
A good course of information is the magazine "Canoe and Kayak". They have articles that are very helpful on making a decision. Another good way of educating yourself is to go to a tryout demonstration of many different brands and styles. Many dealers hold tryouts a couple of times a year.
This beats renting different models because it is usually free and you can compare all models in the same day.They are usually held on a nice lake by invitation from the dealers.