If the memo is to have a title, it should be "Memorandum." The memo should list "TO:", "FROM:", "DATE:" and "SUBJECT:" in that order, as well as the name or item each term indicates. Below that, the body text of the memo can be written; nothing should be indented.
Some memo formats also include a carbon copy (CC:) item for supervisors or other related parties. In addition to the names specified, many memo writers include the position of the addressee and the sender. Though it is not a requirement, body text may be written in inverted pyramid format - the most important things first, smaller details later in descending order. Memoranda frequently use bullet points for lists rather than commas for easy reading and reference.