Also there needs to be parallelism between the two "sides" of the phrase.

"Either go left or right" is less correct than "Go either right or left." Why? Because most people view this as two conjoined sentences. If you say "Either go left or right" it might be construed, perhaps in more complex sentences, that you do not have a verb in the second sentence.

I know Faldage is gonna be on this like white on rice, harrumphing about prescriptivism. And you know what? I don't care! The egg came first, dammit.

TEd