So I hate it when you conjure up a creature, and your enemy does the same thing, and both conjured creatures duke it out.

Or you are fighting a super dragon lord of awesomesauce, and you summon up a creature, and he runs off to attack a rat 5 miles away.

Is there anyway to command a creature to hit a target?

Not really. You can influence them some. If you are lined up with your summon between you and your foe and the summon is just standing there, you can cast a short duration demoralize (or turn undead) spell on them. They will take off toward your foe and when the spell wears off, often be close enough to attack.

If you are standing on a cliff or bridge, sometimes you can cast a summon so he settles to the ground below and attacks your foes down there.

What my elf does is cast a combo spell: Summon clannfear x 30 sec + invisibility on self x 30 sec. She then safely leads Spike straight into the face of her foe. Since she is invisible, she can do this safely and the foe will ignore her.

Yes, other summoners can be a pain. Often it takes a different tactic or approach. My character is sneaky, so she can usually snipe them before they go hostile. Fortunately, Conjurors and Necrodudes are soft targets when they don't know she's there.

I know none of these ideas are super great or really solve the problem, but they do help my character some.

So while your summons and the enemy's summons are duking it out, you blast the enemy with Wizard's Fury. Or you go invisible and sneak up on him, and stab him with a poisoned dagger.

This is the reason I rarely use summons. Too unpredictable

On another note, it′s quite fun to attack Jeanne′s scamp which she conjures up every now and then in the Mages Guild in Bruma :hehe:

Well one theory I had was to just cast silence on the enemy thus resulting in no summons from them, or preventing their cast.

But when I open with a silence spell on say a Necro, as soon as I can it on him, he instantly casts his summon and starts blowing away spells.

What gives? I know when I cast silence and it hits they turn a greenish color.

Necros carry magic scrolls. If they happen to have a summon scroll, they'll use 'em.

They must have a ton of scrolls cause one guy I was fighting was silenced the whole time and summoned 4 creatures throughout the fitht.

I kind of prefer if summons attack each other, but if it bothers you a mysticism dispel spell on target (not area of effect or you might dispel your own summon) or on touch the others summon if the dispel is powerful enough should banish the opponents conjure back to Oblivion. bliviongate:
I haven't personally tried it so I don't know how much mana/magicka it would take to keep dispelling something that gets conjured but it should be less than what it costs them to bring it and stop them from doing damage to you while they're busy conjuring and your minion attacks them.

Use a frenzy spell on the other summon and watch as it (hopefully) returns-to-sender.
Failing that, make one of the summons have a short 100% chameleon spell put on it and the other one should lose interest in the now invisible summon.
And if that fails, cast dispel on the enemy summoner and the enemy summon should vanish.