A Good Grip. While the head size and weight depends on your skill level and desired qualities, the handle should fit comfortably in your palm. You should be able to fit an index finger in the gap.
When you serve, it helps to lower your hand on the racket while maintaining your grip.
Looking at the side you are serving from, stand here and prepare to serve across the net to the opposite side of the court kitty-corner to the area under my palm.
When serving overhand, toss the ball above you and just a little in front of you. Wait for it to fall and then hit it over the net. Everyone serves differently, so find out which was works for you.
This is the stance you take waiting for a serve to be hit towards you. This is in the middle between forehand and backhand returns. Being on your toes allows you to be ready to move in any direction.
Two Ways to Return a Serve: This photo shows me using a two handed forehand. I normally use one hand to return a serve on my right side, but it is more stable to use both hands sometimes.
Second Way: Pictured above is a me using my backhand (when you hit from your left side). It is recommended to use two hands for added power and accuracy, but can be done one handed.
In a doubles match, the second person will stand on this service line on the opposite side that you are serving from.