How to get sharper pictures with this lens?

In February I bought a used gray market Nikkor 70-300mm f/4-5.6G lens. I love the range it gives me, but it seems like I can never get my pictures to turn out as sharp as I want them to be.

I've tried stopping down all the way to f/22 and using my tripod with a remote shutter release. No matter what I've tried, or what focal length I'm using, the focus is always soft and the edges of things in the picture are kind of fuzzy. It happens even if I'm using autofocus. Is there anything else I can do to try to improve the quality of the pics?

Added (1). I've tried shooting at f/8 on bright, sunny days and the result is the same.

I can't post any examples right now… All of my files are on my external hard drive, which my mom borrowed from me for the weekend. I'll try to get her to email me a few of them tonight, or I'll go out and shoot some more with various settings tomorrow and upload them to Flickr.

Added (2). Also, I know this is one of the cheapest lenses Nikon makes. I didn't expect super high quality from a lens I spent $80 on, but I was hoping it would work to get me through a couple semesters of photography.

The 70-300 G is definitely one of the least expensive lenses to get you to 300 mm, but there are some tradeoffs with the low price tag. I've found my lens to be pretty soft throughout the zoom range (mine is soft even stopped down) and relatively slow to focus (D70). The lens performs best in well lit environments and is capable of taking high quality pictures, but may require more post processing and effort than faster lenses to achieve these results.

I bought the lens mainly to get the zoom range at an affordable price, but plan to replace it in the near future (probably will sell the lens). The build quality isn't the best, but it is still pretty durable. Recommended for beginning photographers or photographers on a budget (like myself), but others may be left wanting more. Still, it is sold at a great price.

Don't stop down to f/22 you'll have difraction issues that'll make the image sharpness deteriorate.

The sweet spot for lenses is usually around f/8… If you have a U/V filter fitted, try removing it to see if it improves sharpness.
If you are using the ED version of this lens you should do OK… The cheaper straight G lens isn't anywhere as good but should still produce fairly sharp images.

The tripod is a good idea but if the shutter speed is around 1/2 to 1 second the action of the mirror slapping up can create an unsharp image.

Can you post a link to an example?

It sounds to be a good lens, but if second hand I won't wait for better results from it. Also maybe it's old. You can send it to refix lens elements. Or you can make use of the fuzzy edges.

One of the cheapest Nikkor zooms there's, and it doesn't have the ED elements of the updated VR version. Don't expect anything superb at any focal length or aperature.

Closing down the aperature to f22 can give even worse results from diffraction than shooting wide open. F7.0 to F9.0 should be the sweet spot for your lens.

Use it at f/8 on a very bright, sunny day.

Which model Nikon do you have?

This is not an AF-S lens, so if you have a D3000, D3100, D5000, D5100, D40, or D60, it won't autofocus that lens. If you have one of those cameras, you need to manually focus the lens.