COOKING THE MEAT
In this age when more and more meat comes from younger and younger animals, the fresh meat that we buy in the stores is by nature tender. Well, unless we buy one of these tough cuts of course. Generally though, the meat we eat today is not really the same as the meat that our grandparents ate. This requires some extra thinking when attempting to cook such meat and following the old recipes that stick to long-cooking methods like stewing or braising. Remember that the longer you cook a tender cut of meat, the less tender it will be - it will become more dry, especially if the fat content is very low. The recipes that your grandparents used were often designed for meat of old animals, which were no longer practical for other means of production (e.g. milk, working in the field, dragging the wagons, and such!). The old meat is more tough, especially if it comes from a well-exercised animal, and so it requires long cooking time to make it more tender. Their fat content could be higher as well, and as fat melted in the heat of cooking, it provided more juiciness even if the muscle fibers of the meat became dry after a few hours in the hot pot. Today's meat is not like that. It is more tender and less fat. Thus, it is very easy to overcook it.
Now, once that happens - overcooking, that is - you can still attempt to save the meat by cutting it into small pieces (if appropriate for the dish!) and then simply immerse them in your sauce or other aromatic liquid that comes with the dish. The small pieces of meat, even if cooked dry, will adsorb some of the liquid to their surface and make it taste more juicy. But that's the ultimate solution, if everything else fails, so to speak.
Let us then discuss some of the "old" meat cooking methods and how they worked, so you can apply them with more care if you want to use a tender (or why not a traditionally tough) cut of meat in your dishes.
The most common method to tenderize the meat is by banging it with a special sort of meat tenderizing "hammer". Also, grinding or cutting the meat will provide a substantial amount of damage to it, so the tissues will become more tender even before we cook the meat.
Another way to tenderize your meat is to put it for some hours or days into a marinade - a sour liquid that can be based on vinegar, wine, or other acidic ingredients that will weaken the muscle fibers and make them more moist. Marinade can be flavored with fine aromatic ingredients as well, so it will provide more flavor to the meat. The good thing to remember here is to avoid large cuts of meat that will be cured only on the surface and not in the center.
Finally, to avoid dryness and make the meat more juicy there is one very old method to play with. It is called brining, and it originates somewhere from Scandinavia. Brining essentialy means immersing the meat in 3-6% salt solution for some hours or days before cooking it. The more salt and the longer brining time will of course give more effect. Salt acts as a modest water attractor (just like in our cartilage joints), but it also helps to loosen up the meat structure by breaking up the protein's natural state of being (no need to go into the chemistry here). The result is a slightly more juicy and more tender meat. Obviously, the high amount of salt will make the meat salty, but this can be balanced by other ingredients.