In most countries the basic format for a business letter is just like the format needed to write a business letter in an English speaking country. Most of the time, the questions come up with vocabulary and word choice in the body of the letter, or greetings and salutations. I found a website that can help you answer these questions in a format that is also easy to understand. http://www.learn-english-today.com/business-english/bus-letter-guidelines.html (I've also copy and pasted the information into a word document that you can print out https://drive.google.com/file/d/0B91PszKtVKWkcVY2X2pfNEF3NFk/edit?usp=sharing )
Here's a great video to watch online about how to write a business letter which also contains advice about what NOT to write in a letter. https://www.youtube.com/watch?v=egeyiUpFsaw
I hope this helps!