And before jumping either to CSS hacks or CC remember that often there are ways to avoid hacks altogether. As Andy Budd once told at his talk at @media conference in London it is so sad that too many webdevs think that CSS hacks is the normal way to do things. They are not. Instead of thinking "what hack shoul I use to fix it?" one should first think "how can I rework it to fix it in IE without hacks?".

When there are no hacks there is no problem of "where do I put my hacks in?" to solve.

I think I have used only one hack: _width to solve broken box model in IE5 (which is no longer relevant. And I don't count setting display: inline on float to avoid double margin bug in IE6 as a hack.)