A simple way to maintain a professional image is to make sure all your written material is spelt correctly, is grammatically accurate and displays the right punctuation. Stray apostrophes, random quotation marks and obvious misspellings distract from your message and give a bad impression of your abilities, even if you don’t specialise in communication.
Don’t just rely on your computer spell check function, as there are cases where spelling and punctuation will depend on the context of your message. Read over your communication carefully, and then have someone with sound knowledge of spelling and grammar double check any signage or important documents before you print, send or order things.