Choosing a tennis racket takes as much research and information gathering as selecting a model of car. There are literally hundreds of different models on the market and it takes some work to find the one right for your particular body type and style of play.
The first thing to consider when selecting a racket is usually the size of the frame and the grip size. These vary significantly according to the player's body and hand size. Children and small adults will usually need a smaller length racket and a smaller grip size. Most tennis professionals suggest that children begin playing with a 26 inch racket and a 4.125 inch grip size. As they grow, both of these sizes will graduate along with the child. Most adults play with a standard size racket length and choose grip sizes anywhere from 4.375 inches (most popular for women) to 4.5 inches (more standard for men).
The next criteria to consider when choosing a racket are the weight and body size of the racket. Mostly a matter of personal choice, these two characteristics vary widely. Many of the lower level ability players like to play with a wider body racket, which is more forgiving. Those players who have a greater grasp of the game tend to choose a smaller, denser frame which provides more power and flexibility and yet is much harder to play with. While also a matter of preference, most women and children perform better with a lighter racket which allows them to move it faster through the air. Big, powerful servers and those people with heavy flat ground strokes usually select a heavier racket which will provide more power.
There are several racket manufacturers with product on the market, and all have their devotees. Finding the maker that is right for you really requires that you take several different brands out for a test drive. Almost every tennis pro shop allows you to "demo" a racket for a nominal fee. Likewise, larger online tennis retailers allow customers to demo rackets for only the cost of shipping. There really aren't any brands that are superior; it is more a matter of personal preference. The most popular makes today are Babolat, Prince, Wilson and Head. All of these manufacturers have a wide range of rackets that vary in size, head weight and stiffness. It is just a matter of finding the racket that helps you perform to your best ability.