Hi Craven,
Since you are just learning tennis...perhaps one of the most important things for you to know in the beginning is how to condition your body before you get on the court. Tennis is a very high impact and intense sport.
I
ALWAYS stretch beforehand. From the top of my body, starting with my neck all the way down to my toes. It only takes a few minutes and your body will appreciate it
After I stretch I like to hit a few controlled shots at mid court (or against the net) just to warm up. Gets the heart rate up a little bit.
Off court.......as a part of my exercise, I like to jog. Personally I think jogging is one of the best forms of exercise for a tennis player as it not only gives your heart a good work out...but your legs also.
I guess one thing I would say to you as you are learning to play is this:
Learn to focus on your opponents weakspots. Everyone has them. You will quickly spot them.
One of the biggest ones, is a high backhand. Most people are out of their comfort zone the higher up they have to jump to hit the ball. You can take advantage of this by learning to hit the ball high and slow and hit it well. What you want to happen when you do this is cause your opponent to be behind the baseline with their weight on their back foot.
From that point they will generally hit the ball short or into the net.
If you have access to a tennis ball machine.....they are great to practice on when you can't be on the court!
Good luck! You'll love tennis!!!!