Basic Logic: Swim the Australian crawl (AKA "crawl" or the misnomer "Freestyle"). Swim for technique first and foremost. Swim for speed later.
Of all the disciplines in triathlon, the swim requires the most technique. A strong or fit person swimming will lose to a technically good swimmer every time.
Body position is the most important element to being a good swimmer. You must master the ability to keep your heel, hip and shoulder level near the surface of the water at all times. This is primarily achieved with head position. While swimming, keep your head in the water so that just a small circle at the back of the head is exposed to air. As you are swimming, the water line will hit the crown of your head and not your hair line. The secondary element to being level is "pressing the buoy". The torso of the human body is filled with air and that torso acts a bit like a buoy in the water. Play with the idea, and the feeling, that you can press the front of your chest down farther into the water and by doing so, raise the hips and heels nearer to the surface. The best drill for this is "skating" where you are on your side, with shoulders stacked on top of one another, and one arm is extended in front of you - it's as if you are the long, super straight blade of a skate.
After body position, "the roll" is likely the next most important piece of the swim puzzle. Swimming flat on one's stomach is slow and inefficient. Let the body roll from side to side while swimming. After the arm has finished its recovery and is ready to enter the water, let that entry trigger the roll. As the arm falls forward power can be gained from the hips as they tip or spin onto the new side. As the leading arm extends completely in front of the head, the body finishes its roll and the hand stretches way out to the body's maximum length. That moment, where the arm is fully extended, and body is on its side and at it's longest, should be held for a moment. This gives the swimmer a time to glide and will increase his/her DPS or distance per stroke.
When that long arm finally gets to go into propulsive action it does so in 3 distinctive phases. The catch; the arm bends at the elbow and the forearm and hand begin to point towards the bottom, The arm sweep; with the elbow high, the hand and forearm pull through the water, not straight, but through a slight elliptical pattern that crosses under the belly button. This is complimented by the progressive roll of the body. The finish; as the hand nears the hip area it pushes straight back toward the feet and doesn't stop pushing until the arm is fully extended. The only job for that arm now is a nice relaxed "recovery" where the elbow is high out of the water and the hand and forearm are as limp as a wet noodle.
Re: Kicking, keep it to a minimum, find your power in the arm's pull and the hip's pivot.
Re: Breathing, do it often - both sides or one side but maintain level body during breath.
Re: Fins, paddles, etc., try and limit these items, you can't use them on race day.
Re: Back stroke, it compliments the crawl nicely and will give a good stretch.
Re: Goggles, a pair that will hold briefly with suction alone (no strap) are ones that fit.