Which error did you see most often in 2019? Was it a missing comma? A misplaced or missing apostrophe? A lack of subject-verb agreement? A word used incorrectly? The error I found most often in work projects—especially copyediting presentations and manuscripts—is described below, with one bonus error.
The error is inconsistency.
For example, it's using Department on Slide 1 and department on Slide 2, followed by Dept. on Slide 3. I recently reviewed a PowerPoint presentation with just such an error. Of course, Department, department, and Dept. are all acceptable depending on the project and the communication medium. The error is the inconsistency. It can distract close readers and attentive audience members, who notice the differences and wonder about their significance.
My solution to avoid these kinds of errors is to create a style sheet--and to follow it. That means to decide which version of department works best for your purposes and to use it consistently.
For more information on style sheets, read my post "Why You Need a Style Sheet and How to Create One." I also recommend my online, self-study course Proofread Like a Pro.
The bonus error I saw all year long was the capitalization of words in the complimentary close.
This is wrong: With Best Wishes,
This is right: With best wishes,
Only the first word of the close should be capitalized unless you have another reason for the capitalization, for example:
Best wishes for a happy Christmas,
I'd love to hear from you. How do you avoid the error of inconsistency? Which error did you notice most often in 2019?
Happy new year! (There's no reason to capitalize new or year.) I look forward to writing for you in 2020.