Today I’m speaking not only to language learners, but also to native speakers: please proofread when you write. This means read your text again, look for errors, and correct them. If possible, ask someone else to proofread your text, too. A well-written paper shows you have good ideas; a correctly written paper shows you understand complex situations.
When reading texts written by native speakers of the text’s language, I often see mistakes in mechanics, and occasionally in spelling and grammar as well. The reasons for this may be the writer’s lack of understanding of the rules and practices of writing, carelessness on the part of the writer, or sometimes, their apathy toward the idea of writing with proper style.
But whatever the reason, the result is the same: these errors make it difficult for me to take the text seriously or to believe what the writer is telling me. And unfortunately, this happens a lot. I don’t just see it in text messages or on Facebook, but in professionally written and/or published texts, in news and business-related magazines, and even (regretfully) in some language-learning materials I’ve used in the past.
If you’re writing a text and you get stuck, and you’re not sure what the rule is for your situation, please ask someone or look it up. You can ask me; I know a lot about these things, but I admit I sometimes have to look things up, too.
If you’re reading a text and you find mistakes, please inform the author or publisher if a medium for such communication is available to you. (Of course this includes me! I would like to think my English is quite good, though we all make mistakes, but I know my French is far from perfect!) More often than not, the writer will be grateful you’ve pointed out an error, that you’ve helped them to look more professional, and that you’ve made the content of their writing more easily accessible.
Scroll down to “Follow AD” at the bottom of this page to get all of my posts, which, hopefully, I will have proofread carefully before posting. Also, feel free to leave a comment about an error you’ve seen, how you felt when you saw it, and what result came of it.
Jeremy Coffman, English teacher & diction coach, Paris
American Diction | Paris 
It really stood out to me when you mentioned that it is important for authors to proofread when they write. Would it be a good idea to have someone proofread writing for you? Having another set of eyes could be a good way to find errors you might miss.
It would absolutely be a good idea, and in fact should be standard practice whenever possible.