I bring you:
Ten Common Mistakes that dismiss you as an amateur, from Holt Uncensored, a blog about the book industry (via literary agent Nathan Branford’s blog).
The following is a list I'll be referring to people *before* they submit anything in writing to anybody (me, agent, publisher, your mom, your boss). From email messages and front-page news in the New York Times to published books and magazine articles, the 10 ouchies listed here crop up everywhere. They're so pernicious that even respected Internet columnists are not immune.
It’s not often that lists like this include such helpful suggestions. Read it. Learn.