Be sure they fit properly. For example, if you want to work on your arm actions, you can grip a float between your legs. Kickboards are large flat floats that you use when you want to practice leg motions. Pullbouys hold your legs in place so you can work on arm movements. If you plan on using floats regularly as part of your training, be sure to purchase a good quality float, because the cheaper ones tend to break up quickly.
Many swimmers like to use goggles when practicing, and even when competing.
If you use them for racing, don't forget to bring an extra pair with you. Make sure you put them on correctly to avoid having them spring back into your eyes. Put the eyepiece on first, then stretch the elastic strap over the back of your head. To keep water out of your ears, you can try wearing plugs that mold to fit your ears. Always be sure to dry the inside of your ears after swimming.