How do you know if your tennis equipment is right for you? Well, when it comes to racquets, there are so many out there, that it can be almost painful at times to find what you're looking for. Some variables to consider can be if you have an arm issue, such as pain in the elbow, wrist and/or forearm. If this is the case, you should definitely consider a racquet that is NOT stiff and/or has a vibration dampening system already in the racquet and/or handle to absorb the vibration when striking the ball. The strings also have a part to do with elbow/arm pain. I'm not going to go into poly vs synthetic and mono-filament, but the softer the string, the better and it would be wise to string looser as well.
Aside from arm issues, there's are issues of power, spin and control. Typically, the stiffer the racquet, the more power you're going to get and the more flexible the racquet is, the less power you'll get. Control and spin usually comes with string patters and type of sting used, along with how tight or loose you string your racquet. The size of the racquet head also makes a difference for the type of game you have as well.
Aside from the above, I suggest that you demo different types racquets and see what fits you best. Make sure you talk to your racquet service professional and have them help you make the best decision possible so you can get on the court and kick some serious butt!