A Request Letter is basically an expression or a question where we request to get particular information. It is also sometimes referred to as LOR - Letter of Request. If you are just asking for an interview then there is no need to enclose a resume.

While writing a request we generally use a formal style which begins with name (Person In charge) and address (Normally company name / address). Then comes the subject line with important details. Here you can also include references if any (Like in case of a request for a job interview). If you have any reference then you can ask him or her about the best way to approach the employer. Then write the body and finally the complimentary close. In the body of the letter introduce yourself and briefly describe the purpose. Also include all the necessary details. Always close the letter in a professional way. Use the words "Yours Sincerely," with your name beneath it. Don't forget to provide the contact information. It should also include phone number, e-mail address and your complete address.

Try to keep the letter short, simple and to the point. Expect that the person going through your request might be a busy person, so take out as much work as possible out of your request and focus on its main points. Always show respect as you are requesting. Always thank the person to whom you are writing for taking the time. While writing to get particular information, always provide a brief explanation about why you need that information. If you are writing for cancellation, then one should provide brief explanation on why you are canceling a particular service. All this will increase the chances of approval of your request.

There are many types of Request Letters http://www.sampleletters.in/category/request-letters/. Here are few examples. A request can be:
For a job interview
For change of address
For Promotion
To fill a survey
To join charity drive
For cancellation
To get particular information
For application form
To increase the credit.