Keeping commits small is crucial. I've been bitten by the "big commit" enough times to force myself to keep commit diffs to a few lines across a few files.

I even go as far as to put "formatting" changes into one commit, and actual code into a separate commit. Formatting changes tend to be things like "unindent this large block of code", or "strip extraneous whitespace".

They can be larger than usual commits, but they allow me to separate functional changes from non-functional changes. And yes, I've seen a non-functional change break working code before.