This is a perfect example of some big mistakes people make buying gear and trying to shoot the photos themselves.
You've got a $1500 camera and a relatively inexpensive "multi-purpose" kit lens to use on it. That's the first mistake.
The lenses make the image... the camera just captures what the lens "sees". You'd have been better off buying a $1500 lens and a $500 camera. The 7D is loaded up with features that are completely unnecessary to shoot still product shots like these. The image quality of a T2i/550D is virtually identical to the 7D.
I'm sorry, but the other mistake is that you sound as if you hardly know an f-stop from a filter from a focal plane. Yet you expect to be able to pick up a complex, professionally oriented camera and produce pro quality work at the push of a button. I'm not saying this to be nasty, but there are 4 year programs at Brooks Institute to learn to shoot products well... Some people think all they need to do is buy a fancy camera with a kit lens and start snapping away. Maybe they might would have done better to put the money spent on the photo gear toward hiring an experienced pro to take the shots - someone who has the right gear and knows how to use it - and left the photography up to them. It's amazing to me... How people today think of photography, that it's just automatic and easy to do. Cameras are actually more complex than they have ever been. And the 7D in particular is one of the more complex models to use.
But, that's water under the bridge, so some specifics...
Some of the previously posted info is wrong... if you want maximum sharpness, you should not stop your lens down beyond f8. After that you'll start to see diffraction robbing fine detail increasingly... you'd see a lot of loss to diffraction at small apertures such as f16 and f22, using a crop sensor camera.
You also need to drop the ISO to 200 or, at most, 400. Since you are using a tripod, there should be no problem with the slower shutter speeds you need to use.... but you might need to use mirror lockup and a remote release or the self-timer.
I'd shoot the product with my full frame 5D Mark II that allows me to use smaller apertures.... though they probably aren't really necessary for a product shot like this, so long as the focus is set up at the hyperfocal distance to put the planes of the subject within the depth of field. I'd use either a TS-E 45mm or 90mm lens, depending upon the size of the item and the working distance available. Sorry, but those are $1000 lenses.
If I were using one of my 7Ds instead, I'd use the 45mm TS-E or a 50mm to 60mm macro lens. A 100mm would require too much working distance.
But you should be able to do pretty well with the 18-135.
Regarding IS... I believe the 18-135mm is one of the lenses where you should turn IS off when you have the camera and lens locked down on a tripod. At any rate, IS isn't needed, so you might as well turn it off just to be safe. Some lenses with less fancy versions of IS can go into a sort of feedback loop when on a tripod, where IS actually causes movement, rather than correcting for it. Some of the more expensive IS lenses sense when they are on a tripod and turn IS off themselves.
You are aware that all images require sharpening, aren't you? Especially 7D images. Straight from the camera they tend to look soft. If you look at the example Sandpiper sharpened, it's a big difference from your original image.
