Let them know which personal characteristics or academic accomplishments you would like them to cover. Usually the choice is yours, although some professors will write only confidential ones. Many employers and professional schools require confidential references, but some don't. You may wish to keep a copy of non-confidential references for your own records. You may want references from faculty members who are retired or away from campus.
Addresses are available from the appropriate departments.
When you write to these professors, provide the same information you would have offered them in a personal appointment. You can also do this by e-mail, but send your resume as plain text rather than as an attachment. Have the original sent to the CDO for your file. Each time you need references sent out, simply complete a reference request form specifying which ones you want us to send and where to send them. We'll copy the original, so you'll only have to ask people to write a reference once.