Looking at your site, some appear overexposed, some underexposed and some just right. In general when shooting landscape you don't want large portions of your image with clipped highlights unless you're doing it deliberately (ex: some high key images). However, it's often good to have some clipping in specular highlights as the extended dynamic range can make your photographs pop. A great way to check your values is to use the eyedropper in the info pallete set to LAB color and read out the luminosity values, which run 0-100. 100 is pure white, 0 is pure black. Also if you put your cursor on the histogram in photoshop you can see what percentage of your pixels are at that value.
As far as histogram shape - it is completely dependent on your image. Some images may be 80% shadows, 18% mid tones and 2% highlights or vice versa depending on the content of your composition.
In terms of dark prints, there are lots of good resources on color management that can take you through the process. One tip that isn't always mentioned:
- Make sure you control your print evaluation lighting. It's very easy to think your prints are too dark if evaluating under tungsten lamps at night. If you don't mind spending the coin you can get a desktop print viewer, or you can build one yourself. Another option is to use a high CRI wide dispersion bulb in a household lamp, place your print on a big piece of white backing board and then using a light meter to measure the illumination intensity, move the print away from the lamp until you get in the ~2000 lux range.