
Ok, cutting the suspense. The tender parts of the lamb would definitely be the parts where the muscles of the animal are used less frequently and that would be the ribs and the loin areas! Meat from the ribs and loin are best to cook using these methods: grill, pan broil/pan fry, broil and stir fry. These areas are usually cooked without much liquid as they are quite succulent in texture.
However, the less-tender cuts of the lamb would be those areas where the muscles are used very often, which include: the shoulder/ chuck, rump, round and legs. These meat may be less tender BUT they are very flavourful! The best ways to cook the less tender meat are by: braising, stewing and roasting! Because these meat are pretty tough, they are usually cooked with liquid.
Here's a simple picture of the main parts of the lamb

BAAa-AAaa
The best ingredients to marinade lamb meat for roasting or pan-grilled would be thyme, rosemary (best if the herbs are fresh but dried ones work well too), HP sauce, Worchestershire sauce (I always have to go look at the bottle to check how it's spelled! and pepper and salt to taste. If you want a sweeter taste, put a few teaspoons of brown sugar into your marinade and this will actually caramelise the outer part of your roast or steak! For more flavour and taste, the meat should be left marinated overnight in the fridge but a few hours of marination would be fine and you can always season them again while they are cooking.
Usually a 1-inch thickness steak would require 7-9 minutes on the first side and another 7 on the other side. And the best sauce to serve a lamb steak is non other than mint sauce or a sweet and sour raspberry sauce.
Try the marinade as mentioned above and I'll post something more interesting next, so stay put!