Lamb is a lovely meat, juicy, tender, and cooked to perfection fall off the bone flavorful.
Shoulder of Lamb is very fatty, and works well cooked low and slow, Leg of lamb is less fatty and can be cooked a little hotter, as can sadde of lamb or rack of lamb.
Rub the inside and the outside with either EVO oil or with a flavored EVO.
Garlic and rosemary and thyme go well with lamb as flavors to cook from start to finish.
Onion, garlic, and vinegary mint sauce complement it afterwards, I stay away from mint jelly, (you can use it if you like it), but I find the vinegary mint sauce is a pleasant surprise to most folks who try it.
If you want to try whole lamb, make sure it is wired onto the spit well, and build your fire like a whole hog fire, under the shoulders and hips, but with lamb allow a little more under the shoulders. If you make an outdoor hole in the ground simple pit, and feed it with lit charcoal every hour, a lamb can be spit roasted in 3 1/2 - 4 1/2 hours. if you keep the heat in with sheet steel sides and a sheet steel lid.
Feed the coals under the shoulders and hips for the first 2 - 3 hours, leave a thin layer under the belly. When you refuel after 3 hours, make it a more even layer front to back.
When the skin and meat cracks over the knees and the front legs below the shoulder section, the rest of the lamb will be about 120 -125 internal, (Rare), it will neeed to rest for 30 minutes, in a foil tent to allow the juices to return, if doing whole lamb, I like to take it just a little further, up to 135 ish, I find if you let it hit the 140 as recommended, it will be a little dry for my taste.