Color and tone are subjective, however color management is a science.
Here are a few practical thoughts, suggestions, and links.

Color Management

Color Management is the process of synchronizing color between various devices to achieve consistent and predictable results. In other words if your monitor is calibrated and your printer is calibrated to the same settings your prints should match your monitor. A close match between monitor and prints means you have achieved good color management. An incorrectly calibrated monitor or one that has drifted out of calibration will not give good results.

Monitors

At Luxlab we use Eizo and NEC monitors. Luxlab clients are welcome to view their files on our calibrated system when dropping off print orders. The workstations can be rented for retouching and scanning. We like the NEC 30 inch wide monitor model PA301W-BK. We feel it is the best monitor for photographers. In theory monitors should be set to 6500K with a gamma of 2.2. In practice this is not always the best setting for a specific monitor. After a bit of testing we settled on calibration at 6300K with the gamma set to 2.0 (and we may still tweak this a bit). The lower monitor gamma opened up the shadows to help show detail on screen. It matches our printers better. Different monitors and different calibration tools never exactly match in the real world. This is our conclusion after hours of testing and retesting. We tested identical monitors with close serial numbers, calibrating both, and still have found slight differences even trying different calibration tools and software. And the differences were not consistent, but were repeatable. These differences were only visible with the monitors side-by-side. The more you work with color and printing the more attuned and discerning your eyes become. Our goal at Luxlab is to always have the best calibration.

Shadows and highlights are difficult to judge on backlit screens such as monitors. In Photoshop we manually set the black point and the white point of a file before we start work on color. This assures we have both shadows and highlights free of color cast. We usually like a white point of 8, 8, 8 and a highlight point at 247, 247, 247. This may change depending on the image.

Viewing Prints and Monitor Work Areas

Color is inherent in the light source. Prints viewed under warm light will appear warm. Prints viewed outside on a cloudy day will appear blue. Prints take on the color of the light source they are lit with. Prints need to be judged under the same light source they will be viewed under. Of course one does not always have control of how prints will be viewed, but you probably will not have problems if you use daylight light sources to judge your prints. The area around a monitor should be neutral colors. Not dark, not bright and also not too much tungsten light or any dominate colors. At Luxlab our workstations are surrounded by neutral gray, with darker walls behind us to minimize reflection. We used a color spectrometer to assure our walls and workstation surrounds are neutral.

Color Profiles

We recommend working in Adobe 98 or Prophoto. We find soft proofing to be accurate with Adobe 98 on correctly calibrated high-end monitors. The concept of soft proofing is inherently flawed because a backlit screen is not the same as a print on paper. Still, good calibration and correct profiles make soft proofing a real time saver. We have great results soft proofing in Adobe 98 (only on a calibrated monitor) even though in theory it is better to soft proofing through actual printer profiles. We like to use Photoshop's soft proofing capability to examine out-of-gamut issues more then color issues. Obviously the key is well made printer profiles. Our digital-C custom profiles coupled with a few proprietary hacks to the printer and processing give us a wider digital-C gamut. Our pigment printers run over our network with a dedicated RIP and custom profiles. Click here to download Luxlab Chromira profiles.

Links

Check your color IQ and visual abilities with this very entertaining color test from X-rite.

Ian Lyons explains color management very well.

Real World Color Management by Bruce Fraser, Chris Murphy and Fred Bunting is considered one of the most thorough books explaining color management. It is now available as an electronic download.

Photoshop LAB Color: Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Color space. It is pronounced L-A-B Color. Dan Margulis has written a great book on working in LAB.