Memos are designed to serve a specific purpose. Usually, that purpose will be either to inform the reader of a new piece of information, or to request the reader to take some sort of action. Typically, they begin with a heading something like this:
The following paragraphs will then present the background, or context of the problem, issue or event that is the subject of the memo (Ex: "I have written an essay on the Crimean War for my History 101 class."); the task that is being requested or request that is being responded to ("I would like to receive some feedback on this essay."); and a statement of the purpose of the memo: "I am writing to ask that you have a look at my essay and give me your recommendations as to any changes that should be made.")
Depending on the length of the memo, you may then need to go into more detail. If it is to be a short, one-page memo, you can refer the reader to any necessary attachments ("My essay is attached for your convenience") and conclude with a polite summary: "I would value your suggestions and comments on my Crimean War essay. Thank you for taking the time to consider this request."
At the bottom, make a notation of the attachment:
Attached [or "Attachment"]: Crimean War essay
Good luck with your memo!
[Contributor] 25 / 1,208 476
Here are the objectives of criminal Laws.
- Retribution - Deterrence - Incapacitation - Rehabilitation
Then you break them down into memo format. To learn more the structure of memo-writing, please visit this link: owl.english.purdue.edu/owl/resource/590/04/.
Hope this helps :D