What Should I Write in a Letter? âť’ Information About Yourself.The letter should capture the employer's attention, show why you are writing, indicate why your employment will benefit the company, and ask for an interview. Boost your renewal rates with a foolproof membership renewal letter! In this article, we detail when to use a formal letter format, the different types of formal letters and how to write your own. Sample Authorization Letter. Here are 10 things your welcome letter or email to new members must include plus a template that can be customized for your organization. Open your letter with a strong sentence that defines the purpose of the letter.