I wouldn't say I'm the expert on this, but I am slowly working to change some of the things I had been taught!
It seems like swimming has really changed over the last few decades, and some of the things I had been taught regarding technique seem to no longer be accepted and are in fact discouraged.

Couple of big things I'm currently working on to improve my stroke (I don't have access to a coach so it's primarily from YouTube and the internet and video analysis of swimming greats)!

1) when I was taught improved technique freestyle, it used to be that your palm gets in the water, almost vertical with the thumb going in first. Now it seems this has been found to be bad for the shoulders and not very efficient and now what is recommended is the hand going in fingertips first but all at the same time. Doesn't look as 'graceful' but it seems to be the way things are done now (See Phelps freestyle leg of this IM AT 1:45 ish http://youtu.be/CWTqVI-j6Sk )

2) I believed that the palm should always be kept in a cup position with fingers tightly together so as to push the water as effectively as possible. Now it seems the prevailing wisdom is a sort of claw shap with a little space between the fingers, to increase the surface area of the pull while not losing out from the small spaces between the fingers

3) Stroke rate - I was taught to utilize a slow graceful stroke rate with very long strokes - my view was the fewer strokes taken to cover a distance, the better. Now i realise my stroke rate may be too slow and inconsistent, and I am looking to up it - hope to use the Tempo Trainer or music playlist set to a fixed BPM/ stroke rate to help me out here (http://www.swimsmooth.com/strokerate.html )

4) Rotation - my body didn't roll much during swimming. I didn't think it really should. Now I am trying to bring in body roll quite significantly.

That's just with me! I guess with everyone it will be different things!

I have found the following video VERY INSPIRATIONAL regarding what is possible regarding improvement in time with consistent refinement of technique (eg see from the 3 minute mark onwards). Her gains were amazing:
https://m.youtube.com/watch?v=ojt3nkVoYEU

Swim smooth also have a console on their site you can download onto a PC or an app you can download on iPhone ipad at small cost that shows ideal stroke from multiple angles!

Thanks MacStraw.
What inspires me is that Megan (in the last link I shared) improves her time by over two hours over a theoretical distance of 19km (yep she swam a 19km open water swim at the end - see at the 30 min mark of video) ie an improvement of 12 min per mile! And her speeds at the start of her stroke modifications were approximately my current speed, so It is quite exciting!

Thanks Carl and Macstraw. I have been focusing on your suggestions in the pool. I'm pretty sure that I just haven't found a rhythm yet. It's very psychological for me. I have to start out slow enough that I can work into a good rhythm and not get into a pattern of taking huge breaths, trying to keep up with myself and then swimming too fast to maintain.

Carl, I've been thinking about your open water swims and turning your head in time to see a wave. It's actually helping me since I'm in a calm, indoor pool, to remember to slow down and focus on the breath. Mac, I'm going to try your suggestion to Carl about chin to shoulder. I'm pretty sure I swim with my head pretty straight, but this might help me to feel more confident about taking in air. My oldest daughter is home for the holiday, so I'm going to have her videotape me so I can see what I'm doing. I was watching a guy yesterday in the lane next to my daughter's lesson and he was doing what I am aiming for: slow, rhythmic strokes, totally straight body, smooth motion, head turned just enough. At the end of my daughter's lesson, my husband asked if we meet her poolside when she'd dressed and I realized I probably looked like I was stalking the guy in the pool. I'm really visual and I learn by watching other people and then trying to imitate them. I had to walk away, lol.

Great tips here as always. You guys, I may have given up swimming once I realized how much there is to work on, but you guys are so helpful and supportive. (Hopefully I wouldn't have given up, but getting bits of advice has given me things to work on, thus making me look forward to my "swim practice" each time.)

Thanks,
~Curly

Curls, you have the right idea. Don't worry about speed or time - go as fast or slow as it takes to get the feel & techniques. Once that happens, you can start to increase the effort. You'll be amazed at how efficient it feels. IF you play a musical instrument, think about learning a difficult piece - you go slowly so that you get the notes right & then speed up to the right tempo once your hands have the notes, patterns, etc. down cold. Particularly with the breathing, you want to stay nice & relaxed, keeping the breathing controlled. You'll see what I meant about having plenty of time to take your breath if you "slow the world down" in your mind - it's actually more difficult to breathe properly when you're manic about it (turning your head too far & too fast, trying to breathe in too much too quickly, etc.).....

Noel - I agree 100%, having things to work on definitely keeps it interesting. Currently, I'm working on my backstroke flip turn (when I was growing up we weren't allowed to roll over & do a front flip turn, we had to come in on our back & flip straight over) & I'm working on a breaststroke pull out, which I've never had since breast was always my worst stroke so I didn't really pay much attention to it.....

Just a reminder, take anything I say with a grain of salt - if you have access to coaches & trainers (especially if they can see you swim) speak with them, ask them questions & run anything I say by them. There is no single way to do anything, every swimmer is different & I certainly don't have all the answers. I will always post any suggestions I have, hopefully they help - but please come back & let me know if something didn't work for you.....