These links are good places to start if you need a good introduction to the business writing genre. They talk about the brainstorming, writing, and revising process that business writers use on a daily basis.
This source gives some tips on how to avoid the common mistakes business writers start out making.
Purdue OWL’s Workplace Writers page provides “resources for workplace writers and people writing during the job search process.” The page covers writing for your audience, how to write effectively in the workplace, employment applications, and specific business correspondences such as press releases, memos, reports, and more!