Aaron has an excellent, long post about the differences between search engines. Well worth reading the entire thing, however I’ll pick out the bits that translate directly into technique.

• Yahoo & MSN like links. They don’t appear to be too fussy about their quality, compared to Google
• MSN likes on-page factors (expect that to change, though)
• MSN likes recent links
• Google trusts older sites, hence the reason people are buying ‘em up en masse.
• If a page is obviously focused on a term Google may filter the document out for that term. I believe part of the reason is a side effect of their duplicate content filter.