Answer:
It depends on the locality and what they want to know. Generally speaking, you should state how long you have known the person, that you know the person is of good character, and, if required by the locality, that he has good reason to obtain the permit. For instance, the person owns a business or routinely carries large sums of money. That particular information may not be required depending on where you are.
My personal recommendation also is, be sure the letter is properly formatted and grammatically correct for a business letter. No offense to you, because I know nothing about you, but if you send a letter in that looks like it was written by a 10 year old, which is much more common than people think, the permitting authority will probably disregard it.