There's already sort of some information on this within our [tag:community-faq]s:

##http://superuser.com/questions/260043/how-do-i-troubleshoot-when-i-have-no-clue-where-to-start

##http://superuser.com/questions/224515/how-do-i-troubleshoot-hardware-issues-related-to-a-computer-freeze-crash

##http://superuser.com/questions/437005/how-to-diagnose-a-pre-operating-system-load-or-hardware-issue

Feel free to either update this with more detailed information, or if the stuff you're thinking of writing would be better suited to a new post, make sure to reference those.