Nowadays HC is piece of cake, not much difference from SC U just running little lower rifts - just be more cautious, more tanky and always use fail-safe skill in case of lags. Also collect backup gear in case of death. For fast lvling and other stuff join communities. For builds check diablofans and leaderboards... and that's all.
Good luck and c u around.
On HC there is less stupidity than on SC - for obvious reasons, but some have to learn hard way