If you don't have a slow cooker, you can also put it in a dutch oven (or just an oven-safe pot with a good lid or foil) in a slow oven.

Try a different cut of meat and cook slowly. When I make beef stew I brown the meat first and then it simmers in the broth with all of the vegetables on low heat for 2-3 hours.

Cook long and low!! Brown meat a but first on all sides.

I think it's all been said, but the most common causes of dry, stringy stew meat are using the wrong cut of meat and cooking the meat at too high of a temperature. Slightly less common reasons are not cooking long enough and putting too much liquid in the pot (boiling not braising).

Stews use cheap tough meats. The process of stewing tenderizes the meat, slowly breaking down the structure of the meat. You are cooking at too high a temperature. The temperature should never get above 190. Stews never boil. It's a slow and low temperature thing.
Here is a link
http://chowhound.chow.com/topics/277121

For red meat, I aim for 12 hours. For chicken you can do less. (I don't know how much less. Maybe 2 hours works for chicken.)

I have read enough Cooks Illustrated to know that the key is very long, moist cooking so the collagen breaks down. The recipes I've tried from sources other than the "experts" never seem to include enough cooking time.

1. Buy a cut of meat that does a lot of work. Shoulder, shank, etc.

2. Tenderize overnight in a marinade of acid and salt.

3. Cook low and slow. 10 hours in a slow cooker is just about perfect.

4. Realize that stew really isn't about the amazing meat. It's about the resulting thick, meaty, soup that results.

Flour and brown the meat before you add any liquid.

I add a can of soda. It doesn't change the taste, but the acids make the meat tender.

I have the same problem with my meat and i slow cook for a ling time nd use lots of liquid. I have been using the packs of pre cut stew meat at the grocery store which I just assumed was already the cheapest cut. Is it not? I was thinking of going to a better cut for my next batch to see if I could be a better textured meat.

Agree with cooking it a long time, low heat, covered pot, with plenty of liquid. If you cook it not long enough, it's tough. My rule of thumb is at least two hours. And agree you can't use meat that's too lean.

You need to use cheap meat. Not top quality meat - it comes out better when it is fatty, etc. Also, are you cutting the meat into bite size pieces? Not too huge. And make sure you are cooking it a good long time.

Watch and learn:
http://www.youtube.com/watch?v=lXHGNDYFgGY

(Need to start with the right cut for sure.)

Without fail the meat turns out tough and stringy. Made beef stew from Real Simple today and the result was nearly inedible. I'm thinking of fishing out the meat and doing something with the leftover sauce tomorrow, but I need some ideas!