Tri-tip steak

We just got a George Foreman grill and I heard you can make a very tender tri-tip. Could you tell me how please?

The tenderness of a cut of meat has to do with how much connective tissue is present in the muscle tissue, the age of the animal, whether or not you've worked to break down the collagen through marination (or another acidic tenderizer), and to a lesser extent, how much fluid is present in the meat. If you're using a direct-source heating method for the meat, as with the George Foreman grill, there isn't a lot you're going to be able to do to ensure it comes out tender, as most of the factors involved are completely out of your control.

The only (easy) way to make a tough cut of meat more tender through cooking is with a moist-heat convection process, like stewing or braising.

Also, there are some advocates of a tenderizing process that involves covering the meat in a thick layer of kosher salt, letting it draw all the water out of the meat, and then waiting until it seeps back down in. Supposedly, the water will pull salt down into the muscle, which helps break down collagen. I tried it with a top round steak once, and I didn't notice an appreciable difference, although I did notice a great deal more saltiness.

There are a lot of things you add or do to it to tenderizing it, but the simplest thing is to make sure you don't overcook it. Either cook the outside quickly and leave the middle rare, or decrease the heat and slowly cook the whole thing without too much browning or burning. Some people oven cook meat all day at a temperature just a little hotter than they want it to be when they eat it. Maybe 180-200F. Then the meat practically falls off the bone. But if you just make sure you don't overheat the surface (or quickly overheat only a very thin layer of the surface, in the case of searing), then that'll still help a lot.

As a guess I would think the George Foreman grill would make tender meat because it has a built in controlled temperature that's low enough to let it cook long enough for the fat to drain out. So you probably don't need to do anything special except make sure you don't leave the steak in there too long. Just enough to get it warm/hot.

A caveat to suferjoe's explanations--

Slow-roasting at low temperatures is a dry-cooking method, cooking meat by circulating dry, warm air around it. If you do not introduce some sort of moisture to the meat, as in through braising or stewing, the result will be extremely tough, extremely dry meat. This is, after all, how jerky is made.