There are a LOT of drills you can do to improve form - but it really depends what is "wrong" in the first place.

Swimming is really about streamline and efficiency. When face down the water should be at or just above your hairline, turning head to side (not lifting up) to breathe.

A few common drills are here: http://swimming.about.com/cs/techniquetips/a/Freestyl_Drills.htm although there are a LOT more.

I typically do fingertip drag, fist, or catchup drills. It helps get back into form when you get tired and things are getting sloppy.

Have a look at www.swimsmooth.com I get a lot of really good info from there. They have a book that I have borrowed from the library which I think is really helpful to break down technique, and give you some good training schedules.
Try aqua-jogging as well if you are training for a run (the run along the bottom of the pool type, not the float with your feet not touching one that requires a floaty belt)

WELCOME!

This..

Have a look at www.swimsmooth.com I get a lot of really good info from there.

.. and this!

I wouldn't worry about speed, distance or anything at this point but rather focus on perfecting form. This includes mastering:

~~bilateral breathing (breathing strategies as you call it, or strategy rather, is explained in details on swimsmooth.com)
~~Catch and pull, meaning proper arm positioning, to become an efficient swimmer but most importantly, avoid swimmers' shoulder
~~Body rotation/positioning
~~Kick technique
~~Proper swim rhythm

Speed and endurance will follow more naturally, once you master all that. Just work on perfecting one at a time at the beginning, as it's hard to get all of them right at the same time. I'm still working on it after 1 and 1/2 year swimming 5 to 6 times a week.

One thing I started doing in the last few months I wish I had started before is some intensity swimming: one length fast, return length slow, another out fast, another return slow, next out fast, return fast, out slow, return slow.. you get the point. This is to practice breathing under intense effort, great for fat burn too apparently - a form of HIIT.

It doesn't matter what you eat before and after swimming as long as you have a balanced, nutritious diet throughout the day/week. Drink tons of water, you may not feel it but you do sweat in the water, it's a workout.

Stitches (is that the pointy pain one feels in the side stomach area?) should go away once you master breathing technique, i.e. blowing bubbles constantly when in the water.

Swimsmooth.com and YouTube.com have been the ultimate source of information for me. I strongly encourage you to check them out.

Feel free to friend me if you want. Good luck!