Timing is everything
The quality of light is crucial to great landscape photography, so you will get your best results by shooting at the golden hour – about an hour after sunrise or before sunset. The light will be much warmer, making the colours really sing. Also, the sun will produce more interesting shadows as it's lower in the sky, helping to bring out texture and shape.
Cloudy days can work too
That said, you shouldn't immediately dismiss cloudy days. These give a great opportunity to shoot water, particularly at slower shutter speeds to get that lovely milky or misty effect. You need slow shutter speeds for this, say to around 1 second, and it gets a lot harder if sunlight is flooding in through your lens.
Don't just go for obvious compositions
We've all seen hundreds of examples of landscape shots with a big rock in a foreground to draw in the eye, long exposure water and a moody sky; while these techniques are good in themselves, they have rather been done to death. Try to get beyond the obvious by trying a higher viewpoint, for instance, shooting at an angle, or even shooting upwards for abstracts.
Work with reflections
Another good way to get eye-catching landscapes is to make the most of reflections. Reflections in water help add symmetry, and also make interesting images in their own right. It's worth investing in a polarising filter, though, to ensure as much detail comes through.
Invest in other filters
Variable ND filters, which fix to the front of your lens and can be adjusted, are great for long-exposure waterfalls and other cool effects, while ND filters are also great for this effect and for balancing the exposure of the foreground and sky.
Try hyperfocal focussing
If you are using a wide-angle lens, a great technique is to focus one third of the way into the scene, with a reasonably narrow aperture, e.g. f/16. Don't use very narrow apertures as a process called defraction can actually make the images softer
Always take support
As you often shoot at narrow apertures and slow shutter speeds in landscape photography, a decent tripod, or at the very least a mini-tripod such as the Joby Gorillapod, is essential to avoid camera shake. Ideally you want your image to be pin-sharp from front to back, and this is hard if you are shooting handheld.
If you are interested in Landscape photography why not join Sue Bishop on her 4 week online photography course Fine Art Landscape Photography