You should also write down the address and any landmark that is close to your address. This will help the vendor to locate your address and hence, deliver your material in proper time.
You need to give the details of the costing and also include the taxes so that there is no confusion later on while making the payment in your letter.
The company's or dealer's name should clearly be written so that there is no miscommunication of the details.
Lastly make sure that you do not make any grammatical and punctuation mistakes in the letter.