Be clear.
Be direct.
Don't be afraid to turn them around if they're making a bad move.
Keep people updated.
Sometimes quickly explaining why you need people where and how helps people steer torwards the right direction a bit quicker as well.

I've found that arrow macros that point north, s, e, w are very effective for steering your group.
Sounds in your macros help as well.

Like the good gentlemen above me well put as well.. don't spam. Clear. Concise.