I have 2 binds for my shaman.
One makes them target my main and follow, the second makes the target my mains target and attack (target=targettarget /assist).

All you then have to do is target something with your main, press the assist macro, then run upto the mob. Cause I'm in Australia and get a tad bit of lag, mobs love to run through my characters, so if I'm meleeing I just run my main through the mob and turn around, normally that leaves the slave on the other side of the mob (it drops off follow as soon as it auto attacks)
Once I'm done i just hit the follow key.