This are my advice for taking sports, just undertook coverage for a series of schools competition and therefore I hope these tips will be helpful to you.
Shutter speed is definitely the main factor. For tennis, you will wanna keep the player sharp and nice, ball can be fuzzy, that's fine. Generally you will need nothing less than 200mm for tennis. I would say if you can get yourself a 300mm prime, get it. If not you are aiming for alot of resolution lost due to cropping.
I'm not sure your tennis game is done in the day or night ? If it's in the day, then shutter speed at anything more than 1/2000 should be no problem with the right exposure, if it's done in the evening or night, switch to manual mode, set your minimum shutter speed to at least 1/500. I'm not sure what camera you are using, assuming it's DX crop, I will say ISO 1000 is your max, or even less, ISO 640 for night time, if it's day time, go as low as possible and keep your shutter speed above 1/500 or increase more because light is sufficient. Aperture for night is always open to the widest. For day, you can close down to f4 if you prefer a sharper image or open widest if you want a nice DOF, but take note when you are wide open, make sure your shutter speed didn't exceed your camera limit which is either 1/4000 or 1/8000. Bring down your ISO to the minimum always in the day
Position. Most games you can stand behind, but not for tennis because you might get whack by the tennis ball. If you are really that lucky, your lens might just get hit by the ball and burst. So always stay alert. You get hit by the ball is just a bruise, your lens get hit means no show. In fact, I'm not sure if the referee will let u be in any of those positions at all. Will there be any A boards ? If so, go behind them
Okay bring a ladder there too. It will be nice if you can get those top down inclination shots above the net in the middle.
I mentioned earlier if you are doing night shots, you set your ISO to merely 1000 or less. Even with aperture wide open and but shutter at 1/640 in manual mode, you will get an underexposed image. Underexposure by 1 ~ 2 f/stops is fine. Just do a boost in software, I can assure you will like the image quality versus high ISO. Even if my D3, I do ISO1600 my max at f2.8 and ISO800. Remember that at high ISO, colour vibrance starts to lost and the amount of noise u get, it is much worse than noise you get when you do software exposure correction.
Focusing, switch to spot focusing, continuous mode and start tracking your players. You will need some practice to track nicely without too much straying all over the place due to breathing movement. If you have the VR lens, use it, it will be extremely helpful for telephotos.
For your shutter release mode in continuous, configure so that you use the AF-ON for focusing and shutter without focus will release. Because there are times you need to just press shutter without refocusing, that will be helpful. Use your thumb to control the focus and index finger to release.
Positioning is critical to getting good expression. While you are at the game, observe the player abit. You will notice some trend on the pattern, like how the player like to engage the opponent. When is the position he/she is moving into a particular motion to strike. These information helps you to predict the next motion he/she is going to act. Some photographers can keep both eyes open and one to look into the field without moving from the viewfinder, if you can, that's good, if you cannot then just relax and observe at times.
Sports most critical moments are actions, actions, and actions. Expressions are big winners for good pictures. So capture them in agony, joy and those stress moments and expressions.
Don't keep moving around just to capture all moments, you end up with none at times. Observe where they will move into, wait for them to be there. Then assume other positions that will allow you to capture different moments. Tennis generally is a slow game verus badminton and table tennis, floorball etc... So there are alot of time for you to get your moments.
Just relax and enjoy clicking away in Continuous Mode
2 cents worth.