Maybe blue hat SEO is when you use 5+ year old SEO tactics and make little or no effect on search engine ranks hahaha. Read Google Best Practices, learn each aspect of SEO indepth and as Happy Geek has said you will be doing SEO the right way.
Same as everybody above
promised results, always less than truthful,
delisted from search engines is a result
google webmaster tools give current correct personalised answers on making your site compliant, google make SEO rules
w3c have code testers to ensure your site is code compliant, w3c make coding rules
bad code, really bad code, does not display in all OS/Browser combinations, and if the bots can't parse it, ranks badly in SER