Scattering "click here" throughout your pages breaks the flow of the text, and makes pages harder to read. Reading text on computers is already more difficult than reading print; integrating links with the flow of text increases readability.

Therefore, create link text that reads well.

Readable links gain importance when a page is presented in another medium. For example, when a page is printed or read offline, "click here" makes no sense, since clicking doesn't work. Making link text readable improves Offline Readability.

Thanks to Mark L. Irons for making this point about one of my biggest pet peeves atm so clear.