I've been struggling with this issue as well.

Despite other's assertions to the contrary, my experience is that even when trying to go 'balls to the wall' all out for control, that very little of what I do is actually control, with the obvious exception of the dailies.

And here's the thing, at low levels you only get one or two dailies. So once or twice a day, for a couple of rounds, you get to feel like a proper controller. Other than that, not so much.

When you read through the guides on controlling, you will find that a lot of the good stuff doesn't even kick in until late paragon. And it isn't until then that (assuming four encounters a day) you even get to have the ability to drop one daily per combat.

----

The above said, the discerning reader will have already figured out that I'm an idiot and don't know what I'm talking about. In that vein, allow me to continue to share some conclusions from my vast stores of ignorance:

Good low level dailies:
Sleep
Web

Grease is also supposed to be quite funny.

Straight away you will notice a theme here, the better the control, the smaller the damage.

I also like Stinking Cloud, for a couple of very good reasons. (1) it doesn't roll to hit, so it is very reliable (2) it can be moved.

There are large numbers of Wizard powers that make difficult terrain, but I haven't yet had a battle where I've thought to myself "what I really need right now is a small patch of difficult terrain that can be easily avoided".

When I'm not dropping dailies (i.e. most of the time), I like to find something else I can do to contribute. Minion killing is a useful role, if a bit of a niche, and there are a couple of low level encounter powers that achieve this by making a temporary zone, and then doing a piddling amount of damage to everything in the zone. It doesn't matter if the damage is small though, because when it comes to killing minions, two points of damage is overkill.

For minion killing, Orbmaster's Incendiary Detonation (lvl 1) and Winter's Wrath (lvl 7) leap off the page at me.

Shock beetle swarm (lvl 3) would also do that, however for your third level encounter power the internet in its infinite wisdom recommends Color Spray, and having chosen something else, I think I have to agree (though grass is greener etc).

I took Hypnotic Pattern instead, (on then theory that 0 damage = awesome control (see above)) and it has been utterly useless, in part because my dice hate me. (see other people's advice about maxing out your attack stat)

Okay, so that covers levels 1-8

What's that? We haven't talked about at-wills? Hmm...

Well, the best ones are probably the dragon mag ones.
Still, there are the ever popular Scorching Burst (which can also do minion killing, in which case you might choose other things for levels 1 & 7 encounter powers). And Thunderwave, though I don't seem to have much luck against Fortitude defense.

But let's talk control for a moment here. You want to control, right? Well, early on (at low levels) your at-wills are going to get a workout. So which of them carry status effects? Lets take a quick look at the ones in the PHB and Arcane power.

Scorching burst doesn't have any control/status effects.

Cloud of daggers and Magic missile don't, though they are both guaranteed hit single target minion killers.

Thunderwave has a small control element in that it might push, but pushing is not as useful as sliding.

Ray of Frost isn't widely popular, but there are people who swear by it. It comes with Slow as a status effect. (Slow in 4th ed caps your speed at 2, see p277 of the PHB)

Phantom Bolt has a small amount of slide attached to it, but it's single target.

Illusory Ambush has a -2 penalty to attacks.

Now then, while keeping in mind that there are probably better options in the dragon magazines, we're straight away looking at Ray of Frost and Illusionay Ambush.

So then the question might be raised, where then does this so called 'control' come from? Well, there's some feats.

Phantom Echoes is a feat that gives you combat advantage for 1 round vs anyone you hit with an Illusion power. So Illusionary Ambush can give them a -2 to attack, and you a +2. This is quite nice. Phantom Bolt is also an Illusion Power. But I imagine this combo is best for pounding away at single targets who are going toe to toe with your Defender.

If you do give Phantom Echoes a look-see, you should consider the Orb of Deception form of Implement Mastery. The base form grants a reroll on an illusion power once per encounter, and the Improved Orb of Deception (paragon feat) also grants the same bonus as Phantom Echoes, but to the first of your allies to attack it (fun for the whole family!). Might be worth considering depending on your group.

Lasting Frost (paragon) + Wintertouched (heroic) achieves something similar, you get combat advantage for a round against anything you hit with a cold power, as well as tacking on vulnerable 5 for moar damage (though as a general rule we should avoid feats that are solely about doing moar damage). Suddenly Ray of Frost looks a lot better.

But once we hit paragon feats, we have Psychic Lock and Spell Focus. Psychic Lock is going to double down on the attack roll penalty (NB: penalties stack!!), and it is worth noting that both Illusionary Ambush and Phantom Bolt have both the illusion and psychic keywords.

But Spell Lock is interesting. It adds a penalty to opponents saving throws. This is especially of note if we went with the Orb of Impsition form of Implement Mastery. The problem is, almost all of our save ends effects are dailies (with the exception of lvl 3 fire shroud I couldn't find any thers in phb or arcane power). Which means that even when you first get to paragon you won't have much use for it. But fortunately orb of imposition has a second effect you can use in those encounters when you're not dropping your dailies.

I may be wrong, but the Staff of Defense form of implement mastery does not appear to have anything special to offer for a controller focused wizard.