From where it was sent
when it was written
what the subject is
If the writer had much education
If the writer was rich or poor.
The inside address should typically begin three to six lines down from the heading in a business letter. This provides enough space for the reader's address to be clearly visible once the letter is folded and placed in an envelope.
Ideally, a business letter should not exceed one page, including the inside address and complimentary closing. A concise business letter is more effective than an overly wordy letter which can distract the reader or completely camouflage the object of the letter.
If you have the address you can easily mail a letter to anywhere, including to Laos. Write the address clearly, spacing it out the way it is written, then the post office will tell you the cost of a stamp.
Clear and simple language, organized steps, and visual aids (if applicable) to help the reader understand and follow the instructions easily. It's also helpful to anticipate any potential questions or problems the reader may encounter and address them in the instructions.
It tells the reader that there is an indication of omission of word(s).
You can state your contact details at the top of the letter - as if you were simply writing to a specific person. Most people put their address and contact number at the top of a letter. It's simple courtesy, Its up to you (and highly useful) to include an email address.
The reader's eye usually goes to the reference line or if there is none, the first sentence of the letter. Let the reader know from the very first sentence what your letter is about.
Yes, it is common for editorials to address the reader directly to engage them on a personal level and convey the writer's perspective with more impact. This can help create a sense of connection and make the reader feel involved in the discussion or issue being addressed.