Answer to Question 1
The two types of inquiry letters are networking letters and cold cover letters. A networking letter is written to a contact you made from networking. The purpose of the letter is to request help with job contacts and career strategies, but not to inquire directly about employment. In contrast, a cold cover letter is written to a contact you don't know. It directly inquires about employment and uses a body structure that is similar to a traditional cover letter.
Answer to Question 2
You must identify your audience's wants and needs. You must talk about how the features and benefits of your product, service, or proposal will meet those wants or needs. You must also present your argument clearly, so that your audience can understand your message.