I have used sirloin, tri-tip, different parts of the chuck, flank steak, etc. The type of meat isn't as important as knowing how to treat the meat. If using a cheap cut, such as chuck, make sure to remove connecting tissue from between muscle parts, and tenderize it by poking a thousand holes (figuratively) with a fork, or using a tenderizing device like a meat mallet. Or you can massage it by hand to break up the tough protien chains in the meat. This is also true of sirloin, tri tip, etc.
A surprisingly tender cut, that is inexpensive as well, is the flat iron steak. It comes from the chuck and can be recognized by the extensive marbling, the petite size, and the line of gristle that runs down the middle from end to end. Simply cut the thin bit of gristle out and you have wonderfully tender meat that is great for stir fries.
Though it's often frowned upon, a good meat tendrizing product. like Adolph's Meat Tenderizer, unseasoned, can make a tough chunk of meat easier to chew. Just learn where to use it, and where not to use it, and understand that it has a lot of salt in it.
Marinades (liquids that contain acidic ingredients) don't tenderize meat. In fact, they only penetrate the very outer layer of the meat, flavoing just tha portion. Brines, on the other hand, are salty solutions, usually with sugar and other flavorings added that do penetrate the meat, all the way through. They add moisture and flavor to meats. And yes, marinades to add flavor as well. Just know the difference between the two, and how they react with the meat.
Look for well marbled meat, with as few large chunks of fat as possible. Try to find darker colored beef, that may even look a bit drier. Bright red and lean equates to less flavor, and tougher meat. I know that the grocers stock their shelves with bright red, lean beef. They do this because Americans have been taught that this is best, and so try to purchace it. Some of the more unscrupulous meat purveyors have actually added dyes to the meat to make it more visually appealing to potential customers.
If the meat is still in the meat counter, it is still safe to eat. And, because the aged, more marble meat isn't what the average consumer is looking for, it may be sold at a better price as well.
If you were to look in the best steak houses, that age their own beef, you would find meat that is marbled with fat, and has a brownish-red color. They age their meat to concentrate its flavor (the evaporated moisture carries no flavor. It simply dilutes the flavor), and let natural enzymes tenderize the beef further. They usually age it until the end pieces of the meat have to be cut off and discarded. They then slice the beef into steaks, and cook them to order for a very premium price.
Every now and again, I go to my favorite meat seller and will find that perfect piece of beef that ahs been dry aged in the meat counter, and has good marbling. When I see it, I snap it up, and the butcher gives me that look that says, that man knows his beef. He occasionally talks to me about how so many people just don't understand how to choose good meat. He also saves choice pieces for me as he knows that I appreciate good meat, and I give him recipes.
Seeeeeeeya; Chief Longwind fo the North