Most letters today will be written on a computer and printed. They should be on A4 paper and use only one side of the paper. If you are writing a letter by hand, only use a blue or black pen. There are different paper sizes that can be used for personal letters, and you can write on both sides of the paper. You should always use A4 paper for business letters. Below are the general rules for writing a personal and a formal letter. When you are completing the exercises, check these lists to make sure you have included everything that is needed. Check the sample letters too. When you have written your letter, it should be placed in an envelope before it is sent. There is a standard way to address an envelope so that they can be read by sorting machines at the post office. You should also include your own address in the top left-hand corner. Then, if the letter cannot be delivered, it can be returned to you.