There is no way to directly control the creature.
Sometimes if I walk ahead slowly it will move ahead of me, though it seems to do that more in close quarters (on stairs or in tunnels). At least once I was waiting for my health and mana to regenerate a little bit before continuing, and he decided to wander down a half flight of stairs and start casting fireballs at some opponents that were previously unaware of my presence.
In open terrain I've generally found it easier to just move forward until you get the attention of some opponents, and then run/jump backwards a little past your creature. You can not retreat too far back, though, or he will start following you.
He seems more aggressive with a ranger head (and a better shield, as he doesn't move around as much during combat). I had him with a Rush Attack / Fatality level 6 head in the fjords (level 20 fighting level 21 imps), but did much better when I switched to a Fireball 2 ranger head. I've just found a Magic Missile / Magic Blast 5 head, but have not had an opportunity to try it yet.
