Write on letterhead, because it looks as though you mean business. If you don't have letterhead, print your letter to the military school on good quality stationery.
Type in your address, the date and the inside address. For the salutation, address it to the person you are writing to and make sure you get her rank right. An example is "Dear Major Chambers,". Note the salutation is followed by a comma.
Be direct. Don't bother with wishing the person a good day or making health inquiries. Start with "I am writing to inquire about the programs available at Eastern Military school" or "I am writing to inquire about my position on the wait-list for the September 2011 term."
Stick to easy-to-understand language. Write short sentences and don't use big words when small ones will do. Avoid jargon, but include military terms in the letter, if they are appropriate.
Remember to start a new paragraph when you change ideas. If, for instance, you want to enroll in the school and inquire about additional programs -- such as boot camp preparation -- be sure to separate the change in topic with a new paragraph.
Sum up your request in the final paragraph of your letter. Then thank the person for responding to your letter and indicate that you look forward to hearing from him. If you are applying to the military school as a student, say you would be pleased to supply any additional information if required.
Close your letter with "Sincerely," or "Sincerely Yours,". This is a formal letter, so "See you," or "Cheers," is not acceptable.
Leave three or four lines so you have enough room to sign the letter. Type in your name and rank, if you have one.