Nice article over at i love typography about what to have in mind when choosing a typeface for your project, whether it’s for web or print.
On choosing type - First principles:
Before we get to the nitty-gritty of choosing type, let’s briefly talk about responsibility. Fundamentally, the responsibility we bear is two-fold: first we owe it to the reader not to hinder their reading pleasure, but to aid it; second, we owe a responsibility to the typeface or typefaces we employ. Good typefaces are designed for a good purpose, but not even the very best types are suited to every situation. Personally, I’m always a little nervous about using a newly acquired typeface. A new typeface is something like a newborn baby (though it doesn’t throw-up on you): don’t drop it, squeeze it too hard, hold it upside-down; in other words, don’t abuse it, treat it respectfully, carefully.