The letter should give information about how the author knows your husband. They can include information about themselves to the extent it is relevant to showing how well they know your husband and/or any special qualifications or credence they have in offering an opinion about your husband's character.
Instead of just offering a laundry list of positive adjectives, it helps a lot to offer specific examples or a story illustrating your husband's positive traits. The examples should be drawn from the author’s direct knowledge and observations (e.g. "I heard around town that he is a good guy and once helped an old lady cross the street" is not very helpful).
Such a letter should indicate the relationship between the person and your husband, and include examples of your husband's good character (i.e. helpful friend, devoted father and husband, etc.) from their perspectives (for example, if they have coached a team together, helped out at a school event, or worked together).
This information is for informational and educational use only and does not establish an attorney-client relationship.
A letter of good moral character for a visa application should show the relationship between your husband and the person writing the letter, and should include specific examples of your husband’s positive characteristics.
FORMER IMMIGRATION LAW PROFESSOR -- LEGAL DISCLAIMER: This answer is offered for informational purposes only. It does not constitute an attorney-client relationship.