This is for hunters...primarily. It can work for any class with instant melee attacks, but they are usually soft-capped, either by rage or energy. So it's most effective for hunters.

When you get your brand new uber weapon and you just bought the skill to use it...what do you do? HIT STUFF! However...by spamming Wing Clip rank 1, you skill up much faster. It counts a swing, thus yielding you 20-30 extra chances to skill up per mob. Use rank 1 to conserve mana and keep on trucking. Your pet will do most of the tanking, so stick to low lvl mobs.