Get permission before making audio recordings or videotaping a speaker. It is simply good manners to let the person know he or she is being recorded, and this precaution can help protect you from royalty claims made later by the presenter if you sell the recordings (as is done at some conferences) or post audio or video clips online.
Ask your campus legal council to draft a release for you. Suggested wording is: "I understand that the audio (or video) rights to the above listed presentation(s) are the property of (your group), who may use such rights, at their discretion, to duplicate, sell, distribute, and market audio (or video) copies of the original recording of the presentation(s)."
Professional entertainers, authors, and speakers who make their living from speaking may not be willing to sign. Instead, they may want to limit your organization's rights and the number of recordings that can be sold, and they may expect a percentage of the sales. These negotiations should take place as part of the speaker's contract. First-time mention of your interest in recording a speaker on the day of show is unprofessional and will likely not be welcome news.
Recording and selling a speech, performance, or workshop presentation without a person"s knowledge could result in an unpleasant encounter with his or her attorney.