You should grip the tennis racquet loosely between strokes, but when you are about to swing, it is better to tighten your hold.
The forehand stroke is usually the most powerful and the stroke that most users want to use.
Tennis balls must conform to the diameter of 65.41‐68.58 mm (2.575‐2.700 inches). Balls must weigh between 56.0g and 59.4g. Yellow and white are the only colours approved by the United States Tennis Association (USTA) and ITF, and most balls produced are fluorescent yellow (known as “optic yellow”) A ball is tested for bounce by dropping it from a height of 100 inches (2.5 m) onto concrete. A bounce between 53 and 58 inches (1.35 ‐ 1.47 m) is acceptable.