Read your letter. As you are reading your letter over a number of times, correct grammatical mistakes, punctuation and sentence structure as you deem appropriate. Make sure there are correct uses of capital letters at the beginnings of sentences and appropriate punctuation throughout. Your sentences should also be sharp, concise and easy to read. As you go through, use your word processor spell-checker to correct spelling mistakes you find.
Review and revise. Go over your letter on a micro level to make sure it follows the correct usage of standard English, while inserting and deleting text to make sure your letter is as clear and persuasive as possible. Review the whole letter, looking for obvious formatting errors. Errors such as unnecessary spaces, template remnants that should be deleted, carriage returns and incorrect indentations. Do your best to remove flowery language and wordy sentences. As stated before, your letter should be concise and easy-to-read, straight to the point, clearly stating your skills and your qualifications, and the best way to get in touch with you. Leave out unnecessary and inappropriate information.
Ask for a friend's help.You may find it helpful to ask a colleague or a friend to re-read the contents of the letter. It is useful to have a second opinion. Ask this person questions regarding the tone of the letter. Ask him whether it displays enthusiasm toward the company to which you are writing and the position for which you are applying. Ask him to tell you whether it is well-written and clear to read. Encourage him to give you advice and suggestions.
Read it as a third person. When your letter is finished, then try to step out of yourself and read it as though you were someone else. This will help you be more objective and determine whether your letter is truly complete. Ask yourself whether your letter's length is right, whether your wording is convincing and if your letter is factually correct and easy to read. Ask yourself whether you would have liked to receive that letter from someone else.
You should end your letter with a short sentence expressing your interest in what you are writing for, once again, along with an "I look forward to hearing from you."