Use a range of grip widths for more or less power, depending on circumstances.  

For more power to accelerate or to paddle against wind and/or current, use a wider grip.  For cruising and speed in calm conditions, use a less wide grip.  The widest grip is determined by where your hands are when holding your paddle horizontally over your head with both hands, forming right angles (90 degrees) at the elbows.  The minimum grip width is determined by holding the paddle horizontally at chest level with upper arms vertical against your torso.  You may mark these positions on your paddle with tape at the outside edge of your hand on the widest grip and at the inside edge of your hand for the minimum width.

To achieve the proper blade angle in the water it is necessary to have a control hand that keeps a fixed grip on a feathered paddle.  Either hand will work.  If you feel more comfortable with a non-feathered paddle after trying a feathered paddle, you can use it with both hands acting as the control for blade angle in the water.  The top knuckles of your control hand should be in line with the top edge of the adjacent blade.  The blade angle is determined by using wrists and/or forearms to adjust it to desired position. The control hand(s) have to maintain the grip.  It should be light and but controlling, primarily accomplished with thumb and forefinger.  A tight grip is unnecessary and fatiguing.

Sit upright or with a slight lean forward, with knees in contact with the deck, lower back firmly against its support, and feet in contact with the foot braces.

Select your control hand for feathered paddle* to use wrist and forearm to rotate the paddle to the proper angle in the water.  Holding the paddle horizontally in front of you, practice rotating it with your wrist and forearm to achieve vertical water entry with both blades.  Note that paddles can be feathered in opposite directions for left or right hand control.

Start with the paddle shaft held horizontally away from your body at chest level, beginning the stroke on the right side by extending your right arm straight out and your left hand coming back to your left shoulder.  Put the blade smoothly, almost gently, into the water near the boat, well forward without leaning into it.  Put the whole blade, but not the shaft, into the water for the entire stroke.  Pull back with your right arm, not the wrist, to pull the boat toward the paddle (not forcefully pulling the paddle through the water towards your body).  As you pull with the right, push with the palm of your left arm forward and across the boat.  The left hand should stay below eye level.  Keep the blade vertical in the water with the most force applied after putting the blade in the water and before passing your hips.  Once at your hips, begin to lift the blade crisply, straight up and out of the water.  Keep raising your right hand until it is at your right shoulder, bringing your left arm into a straightened forward posture with the left blade poised over the water, set to repeat the stroke on the left side of the boat.

*Feathered paddle.  To rotate the blade for vertical entry of a stroke on the non-control side after a stroke on the control hand side, raise the control forearm and bend the wrist backwards as the control hand is lifting away from the water at the end of the stroke.  To rotate the blade for vertical entry on the control side after a stroke on the non-control side, bend the control wrist forward after the blade on the non-control side is lifted out of the water and the non-control hand is moving to the shoulder, and while the control forearm is moving down and forward in preparation for the next stroke.

Practice the basic stroke slowly at first, concentrating on getting the fundamentals right with a fluid, balanced motion.  Remember that you start and stop the push and pull motions at the same times.

Using your torso twist to engage the major muscles of your upper and middle body will add significant power to your forward stroke.  Begin the stroke by twisting your body above the hips to turn your shoulder of the extended arm in the direction of that arm.  In other words, if the stroke is on the right side your torso will be twisted to the left, with your chest pointing at a 45 degree angle from your boat’s centerline, before commencing the pull/push motions.  This extends your stroke by placing the blade further forward.  As you begin your push/pull, start a coordinated release of the twist, uncoiling your body in the direction of the stroke side.  Continue to twist your upper body through 90 degrees during the pull/push motion, ending up coiled towards the opposite side of the boat as when the stroke began, i.e. on the same side as the stroke was made.  

Now your upper body is staged to release the power of your shoulder, back and abdomen into the next stroke by twisting back in the direction of the next stroke at the same time you commence the pull/push.  Repeating this 90 degree torso twist as a smooth part of each stroke, carefully coordinated with the arm motions, delivers maximum forward force transmitted from your body to the kayak at the points where your body contacts the boat.  This force is transmitted primarily through your hip/butt, knee and foot on the same side as the stroke.  To facilitate this you should fit snugly and can press the foot brace on the same side as the stroke with your foot.  

You may notice that the torso twist is doing part of the pull/push part, relieving your arms of part of that effort.  Casual paddling does not require the full torso twist, but its extra power will be available when called on from the accomplished forward stroke.