There are no rules for indenting in a personal letter. If you want it to look neat and want the reader to be able to discern where one subject stops and another begins, then an indent would be a good idea.
When writing a business letter, you usualy don't indent.
A space when beginning to write an essay.
No, but you do indent in a friendly letter.
When you are starting a new paragraph. The first word of that paragraph MUST be indented.
No
At the beginning of each paragraph (except for the first paragraph if you start with a really big letter like they do in some books.)
The first line of each paragraph should be indented to create a clear visual separation between paragraphs in a written document.
The full block format does not indent.
Yes you do. You don't in a business letter.
The return address on a letter identifies the address of the person writing the letter. It is typically placed at the top left corner of the envelope or letter.
When writing a formal letter, the action the author of the letter hopes to achieve should be found in the:
Personal letters differ from business letters in the tone and content. Personal letters are very informal in the use of grammar and vocabulary. It is written in a personal style. There are no specifications for the content or a personal letter, any topic of interest to you and your recipient is acceptable and any amount of details or anecdotes can be used. Business letters needs to be written with higher standards, a more formal grammatical structure, and standardized vocabulary in a professional tone. The content should be focused on the outcome desired, the purpose of the letter, with enough information to achieve that goal without going off target. A business letter should be concise, to the point.