Answers to your Questions
The beginning steps towards any fitness training are assessing your strengths and your weaknesses. Tennis is a mental game. So training is more a mindset than anything. So you will want to focus on clearing out any distractions and focusing solely on training. The athletic level increases with time and comes on its own.
WHAT DO I NEED TO BRING TO A LESSON?
You should bring a tennis racket build to your size and strength. Also it is important that you wear comfortable shoes. Tennis court shoes are designed for tennis players. In tennis there are many sharp turns of the feet as you move. That is why you'll want a tennis shoe with a pivot ball. A cushion that tennis court shoes have at the ball of the foot designed to help players pivot.
HOW DOES TRAINING DIFFER FROM BEGINNERS TO EXPERTS?
Training for beginners will focus on the fundamentals. Experts will focus on that too, but with greater consistency and variety of training methods. Experts will focus on shot selection and making decisions on the court. Beginners will on the other hand will be learning where to stand on the court and how to deal with different types of shot coming towards you.