Which or that?

My general rule is whichever sounds better to you at the time. Just don't use them in place of "who" or "whom" when referring to people.

AnonymousWhat is the general 'rule of thumb' when to use 'which' or 'that' in a sentence?

This is a very general rule of thumb. In general, note that often there is no choice. You must use "that" in certain cases. You must use "which" in certain cases. Therefore, I take your question to concern only the cases where you have a choice. In those cases, use

As others have said, it's completely your choice. I prefer which only because I dislike the way "that" sounds. I recommend not using either very often, though, since the language will begin to sound rather clumsy. In most cases, these things can easily be avoided. The use of these types of words is fine but only in circumstances absolutley requiring them.