What is the proper ready position? It's the position that'll allow you to react most rapidly to the opponent's next shot. It's extremely important in a sport as fast as table tennis. And yet many players have very poor ready positions. They stand up too straight, their feet are too close together, their weight isn't on the balls of their feet, and their non-playing arm hangs loosely at their side like a dead snake.
You want your feet somewhat wide (at least shoulder width apart or more), at least slightly bent, and either parallel to the table or with the right foot (for right-handers) slightly back. The latter puts you in a slight forehand position, but many players actually play their backhands from that position. If you play a flatter, steadier backhand (i.e. blocking and countering), then you don't need to be in a backhand stance to play backhands. The more aggressive you play the backhand (hitting or looping) the more you'll need to be in a ready position that allows you to quickly move into a backhand stance, and so you would want the feet more parallel to the table. Experiment and find what's comfortable for you.
Some players stand in a very backhand stance and greatly favor their stronger backhands. This may work for them somewhat, but it further weakens their already weak forehands. They would probably do better to adopt a more neutral stance.
The racket should normally point at the opponent, or more specifically, where the opponent would hit the ball. This allows you to move to forehand or backhand equally well. Some players tend to hold their playing arm out to the side too much, and so are more ready for forehands than backhands. Try holding the racket more in front of you, even if it means bringing the playing elbow more out in front.
Some players, including me, prefer to hold the racket in a slight backhand position (so the backhand side is partially pointed toward the far side). Conventionally, the backhand is hit quicker off the bounce than the forehand. This means you have less time to hit the backhand. In many cases, this doesn't matter since the stroke is shorter. I find the backhand rushed and awkward when starting from a truly neutral position, while the forehand, where you have plenty of time to get the paddle into position as you turn sideways, is much easier. So years ago I adjusted my ready position so that the racket is in that slight backhand position. This gives you a head start on backhands, while I still have plenty of time to move the racket over for the forehand. I don't normally coach this, but I have advised some players who feel rushed on the backhand to experiment with this.
Weight should be equally distributed between your legs, with your weight centered and balanced, with weight toward the inside balls of your feet. The feet should point slightly outwards, allowing quick sideways movement. Lean slightly forward at the waist. The non-playing arm should be raised as a counter-balance to your playing arm, with the hand at least as high as the elbow.
Want to see examples of good ready positions? Google "table tennis ready position pictures," and dozens of great examples will come up. Pick what looks right for you.
You also want good playing shoes. (A good ready position with bad shoes is like running in dress shoes; not a good idea.) Ideally, get table tennis shoes, which are made for table tennis. They range from what are essentially socks with rubber soles (i.e. highly flexible but little support) to ones with great support. If you have foot problems, are overweight, or play mostly on cement, you probably need extra support. Don't use running shoes, which are designed for running forward, not quick side-to-side movements.
Here's an easy way to find a good ready position. Imagine you are covering someone in basketball. Notice how you automatically spread your legs and bend your knees? This lowering of your center of gravity puts you in the proper ready position, allowing you to move quickly either way. (The only catch - lower your arms, since you don't have to cover someone trying to shoot a basketball over your head!) You can use similar examples for a shortstop in baseball or a goalie in soccer.