Low and Slow
First...always use low heat. If you grill it, make sure that you have the meat on indirect heat. We use a charcoal grill. We start the charcoal in a pile in the center and once it is hot we place all the brickets around the outside edge of the grill. The meat then goes right in the center of the grill where the main heat is not. If you use a gas grill, only light one side and grill your meat on the other side.
Second...If you are using low heat, it will be slow cooking. The most tender meat is cooked slowly.
Third...Only cook it til it's medium-rare for the best flavor and tenderization. Grill on one side til the blood is pooling nicely. Flip to the other side and grill until there is only clear liquid pooling. No blood...just clear liquid.
A point to notice on the medium-rare cooked meat. The center should be a little pink, but hot. It won't hurt you! As long as there is no chance for an oxygen pocket to form there is no chance for contamination.
Only use tongs to flip meat. Don't stab it with a fork or any other object as that will allow oxygen to get to the center of the cut.
And lastly...ENJOY!!! The meat should be so tender that you can nearly cut it with just a fork. Our children love to eat lamb and beef. It's tender...and they don't have to wait for Daddy or Mommy to cut their meat!