Why are my pictures still blurry?

I'm using a sunpak platinum plus tripod with a nikon d70 and 24-85mm lens. I used them to take pictures of landscapes in the snow. The snow was blowing pretty hard but not enough to make the tripod move at all. I was using the retractable spikes too. My pics still turned out a little blurry. I mean I always see crystal clear pictures that people tak of snow and things. I set the focus to infinity and the aperture to the smallest (largest number). Does doing it that way affect the clarity? Should I focus on something in the frame? Below is a link to a pic:

The only thing I can think of is to try a faster shutter speed. The snow is leaving visible trails across the picture, so try something faster. Other than that, the focus seems good to me, the trees in the background could be appearing blurred just because of the snow blowing around.

You may be getting a little bit of blur from the vibration caused by the shutter actuation. Wind can also cause harmonic vibration in cheaper tripods. While the eye doesn't see it the vibration can be enough to cause blur.

The blur is caused by the long shutter times.

The whole time the shutter is open, any movement of the subject will show as blurred.

You seem to be using a check-list to take your photo and are not using some of the fundamental techniques for taking such shots.

1) Using a tripod to shoot landscapes is an excellent idea.
2) the smaller the aperture used, the slower the shutter speed is necessary to get the correct exposure
3) shooting blowing snow will require a shutter speed of at least 1/250th second to prevent blur

You may find taking at least one class in photography will prevent these kinds of frustrations.

From the length of the blurred snow flakes, you shutter speed is around 1/8th to 1/15th second.

Do you also know that the sharpest aperture of your lens is about two stops down from wide open?

http://www.kenrockwell.com/...-stops.htm

More discussion on picking the sharpest aperture on most lenses

http://www.kenrockwell.com/.../focus.htm

The aperture will affect the DOF (depth of field, how much in front of/behind focal point is also in focus). Also, every lens has an aperture "sweet spot" (normally 2-3 stops down from the high end, so around f/8-f/11).

I would have focused on the center fence post for that shot with a f/11, ISO100 (possibly using a flash fill to give the posts detail) to start with… But there's too much sky in that frame for my liking.

This is a prime example of Motion Blur, where the subject (the snow) is moving causing it to blur. To solve this you need to open up your aperture up to the smallest number, probably 3.5-5.6 in the case of your lens. If you put the camera in Aperture priority mode, and set the aperture as high as it will go, then adjust the ISO (prob 100ish if this is outside daytime) until the metered shutter speed is at least 1/200 - 1/250 I would say

Hope this helps

Your f/stop value is too high. Very high f/stop values causes diffraction, which causes your pictures to be slightly soft. In fact, any f/stop beyond f/8 will slowly degrade your image. Unless your shooting a difficult scene that calls for maximum depth of field possible, always stick to f/8 or lower.