Depending on where you live in the world, sheep can be as common as shoes or as unusual as a lama. Wherever you do live, though, you've got it relatively easy if you want to draw a sheep. They are covered in wool after all, so the basic form you want to start out with is an oval lying on its side. From there you add a head, which is a modified triangle (because their mouths make a little square at the sharp point of the triangle). Then you add to long loppy ears, some short legs with black triangle hooves, and a little poof of a wooly tail. Voila!
Sheep are fairly mellow creatures, like cows, but they are capable of getting into some interesting predicaments. Some of them are agile climbers, which is abundantly obvious if you've ever had the good luck of watching them scramble over rock walls. In fact, they are so good at it that there is a special breed of sheep with super short legs, just because the shepherds got so tired of chasing after runaway sheep that they bred them so they couldn't get away so easy.
Sheep are ideal for landscape drawings, like cows, and they ought to be drawn in groups, as sheep don't really care to be solitary, unless they're a ram.