I have always maintained that anyone who is serious about photography and would like to share his/her work must have his/her workflow tuned to the proper standard at every stage of his/her workflow. The philosphy is simple – from the minute you click the shutter till the time you share the image with the community the image must look almost the same at every stage of the digital photography workflow. There should not be any significant changes in contrast, colour shifts or loss of highlight or shadow details. This obviously applies to those viewing your shared images through their respective monitors too. Otherwise any technical comments on the image will not be valid.
It is imperative that you set the color setting right even before you start using Photoshop. Photoshop’s default color space is sRGB which is the correct color space for Web posting. However sRGB is really a very limited color space, much smaller than what printers can actually produce. I strongly suggest you to change this to Adobe RGB (1998). You do this by going to Edit> Color Settings.