1. Less Clouds: even in summer (at least here in Ireland anyway) there is no shortage of cloudy overcast days. Whereas at this time of year, as it gets frostier, you can find beautiful blue skies. This is especially true if you're taking pictures of rivers, lakes and the sea.
2. Less Crowds: During the summer it can be practically impossible to get nice moody landscape shots, especially in areas that are popular with tourists. After all what's the point of going trying to capture the awe and majesty of nature only to find it over-run with camper vans and station wagons. Go there in November however, and you won't find a soul.
3. Later Sunrises: There are two types of photographers, the ones who are more than happy to get up at 4am and hike up a mountain and set up their tripod, and then there's guy's like me. See that's the thing with darker mornings, you don't have to get up so early to catch the sunrise. :)
4. Earlier Sunsets: And of course you don't need to hang around waiting for the sun to set either.
5. Contrast and Shadows: In summertime it's too bright, in winter it's too dark and in springtime it's still too wet. That's why I find autumn the perfect time to take landscapes. I also advise flash, even in daytime. I just use the camera's inbuilt flash, which is adjustable and not too bright, so that the foreground is illuminated better, particularly when you are framing objects, or if you have a moody, dusky background but also want to capture the foreground. (Though try it again without the flash too, as you might get some nice, unforeseen silhouette effects.)
6. Shoot at midday!: Generally speaking it's not always advisable to shoot at midday but it’s actually not a bad idea at this time of year. Though the sun can be quite bright on crisp, frosty days, on most days the light is less severe so you don't have that intense brightness directly overhead washing out your shots. So if you want to take panorama shots go out and take them now!
7. The Colours: Autumn (that's Fall to you North Americans) is the best time of the year for colours. I love it. All of a sudden landscapes and cityscapes that looked empty & grey are alive with colour. This is not just the best time to shoot in the country, you can also get great shots in parks and city squares. Just find a good spot, frame it well, then shoot. Experiment with different white balance settings and go for long, deep exposures or try bracketing different exposures as you go along. If possible shoot in RAW format so you can bring out the saturation and vibrancy of the leaves.
8. Winter: As the month progresses, the leaves begin to fall and the weather becomes ever more chilly. Frosty mornings are perfect though, as they ensure bright, blue cloudless skies. Get up early and you can get frozen dew on leaves, or those frosty fronds upon windows - great for macro shots - or my personal favourite, the crystalline strands of a frost-covered spider web glistening in the early morning sun. If you want to take landscape shots with frosty grass, try longer exposures, to capture the crunchiness of each blade.
9. Fog: For creating mood and atmospherics, find a lake or river, or an evergreen forest, at sunrise & go for those "fantasy" shots. Experiment with exposure, however, as every situation is different and don't be afraid to break the rules. Over-expose, underexpose, or even try shooting INTO the sun for a change. It's fog; you're not supposed to see everything!
10. Winter wonderland shots: The later you leave these the busier it's going to be, especially in towns and cities, as the xmas shopping rush kicks in. When exposing try locking exposure on different elements to see which comes out best, especially where snow is involved. If you lock on the snow the rest will be dark, if you lock on the darker parts the snow will come out like magnesium so try find a happy medium. Avoid flash if at all possible, and if not, try and diffuse it or use natural light. If your camera has white balance bracketing USE IT! It might also be a good idea to experiment with your polarizer too, if you have one, and if not maybe you could put a polarizer on your xmas list.