This is a compilation of everything I've read about proper swim technique, a synthesis, if you will. In the interest of exploiting your strengths and strengthening your weaknesses, I'll provide these guides, which I originally wrote for my multisport club at Genesis.
Head position: Look straight down, your nose pointing towards the pool floor, when you're practicing swimming. Your chin shouldn't be tucked or lifted, but held in a neutral position. Allow water to almost cover the back of your head; in other words, hide your head below the water. As you rotate from side to side, try to keep your face pointing at the pool bottom (except when breathing, of course).
Body Position: Always preserve a straight body line in the water; head, neck, shoulders, stomach, and hips should be in alignment, as though you have a steel rod passing from the crown of your head down to your hips. Don't allow your back to bow, or suck in your stomach too far. Press your lungs toward the bottom of the pool. Your lungs serve as a fulcrum for the rest of your body, so to get your body horizontal while swimming, you have to push extra hard on the head/torso end of the lever. The overall sensation should be one of swimming downhill. If your legs are low in the water, they will produce more drag (which means you'll go slower!) and pull you down, forcing you to spend extra energy by kicking in order not to sink. When swimming on your sides (or when rotating from side to side), focus on pushing your armpit down. Reach towards the pool wall immediately after your hand entry and before your catch (but not so far that your hips get out of alignment). Think about squeezing your body through the smallest hole possible.
Hand Entry: You swim with blades, not with fish. Your hand should slice into the water somewhere between your goggle line and a couple of inches in front of your head; they should not fully extend, then flop into the water. It is more efficient to finish extending your hand under water, rather than extending fully in the air. Your hand should enter directly in front of your shoulder, not at the center line of your body (i.e. in front of your head). Keep your arm from crossing over. Pinky should be highest of the fingers during entry.
Pull: Pull doesn't begin until just before your opposite hand enters the water. Don't let one arm sink as your opposite arm recovers (particularly as you breathe); one hand should always be extended in front of your body (this is called front quadrant swimming). Fingers of your hand should be together, thumb straight out to the side. Elbow should be higher than the hand at every point of the stroke. When initiating your pull, think of grabbing a handful of water, holding onto a chunk of “hard” water, or anchoring your hand and swimming past it. Use the rotational force of your hips and torso to pull yourself past your hand, rather than pulling your hand down towards yourself. Your hands should pull back past your hips, your thumbs brushing against your thighs as your hands exit the water. The last part of your stroke is a push back past your hips, not a pull up out of the water.
Recovery: Keep a high elbow throughout your recovery. Imagine that your elbow is attached to a puppet string that is pulling it up out of the water. Make sure that your whole arm is fully clearing the water with every stroke.
Breathing: Do not lift your head out of the water to breathe; raising your head will screw up your body position. Use a slow, controlled exhale throughout your stroke; do not (at any point) hold your breath. End your exhale before turning to the air to breathe. Every second of time you have your face exposed should be used to draw in air; don't waste it on finishing your exhale. Practice bilateral breathing (breathing to both the left and right side, not just to your dominant side) whenever possible by breathing every third or fifth stroke.
Kick: Avoid using an extra strong kick to make up for poor balance and body position in the water. Feet should stay just below the surface of the water, your heels barely kissing the air; you shouldn't be kicking up a lot of foam.