Writing is easy, the challenge is to make other people understand what you say.
As the writer, you are responsible of reviewing your work. Documents without format standards are unacceptable. Errors in spelling or punctuation should be reduced to none. Communication is hard already, you do not need other things to make it more difficult.
I have found some great advices to improve my writing skills. Everyone who is writing should follow them as well. Applying those may not turn you into a best-selling author, but it is, at least, a sign of respect for your reader.