I use only two filters, a polariser and a neutral density gradual grey filter by Cokin. Its called neutral grey but it isnt really, light hitting it at an angle or using more than one filter introduces a purplish/pink cast.

The graduated neutral density filter is usually as important to the landscape photographer as the camera and lenses. It is not a 'trick filter', it compensates for the limitations of film and digital sensors so you can balance bright skies and dark landscape.

The cokin filter holder lets you position the transition between the grey and clear parts of the filter easily, I have modified mine by sawing off the front filter holders so it only holds one filter at a time, this is necessary when using very wide lenses.

Most of the coking filters scratch more than a cat with fleas, I usually get two months out of a filter before its too scratched to use but if your ultra careful they could last much longer.

If your considering buying the Cokin holder, always get the 'P' version, the 'A' only fits smaller lenses but the 'P' system will fit almost all lenses with adapters.

Photographers using film carried other essential filters that are no longer necessary with digital, warm up filters can be substituted by changing the white balance on the camera to 'cloudy' or 'shade' and the red and orange filters every self respecting B&W photographer used religiously can be mimicked and even bettered by using the colour channels in photoshop. B&W film photos which most people presume are 'pure' were usually very heavily filtered and manipulated before and after taking the photo, thats why simply moving the saturation slider will not give your B&W photos the kind of 'pop' that you see in galleries.

Apart from filters its just a case of waiting for the right conditions, I cant stop myself now looking up at the sky and evaluating the quality of the cloud in the sky whenever I leave the house and you learn to anticipate whats likely to come next.