Use the Reserve service where appropriate or warn Reference librarians ahead of time about an assignment in a specific reference source. Avoid scavenger hunts. Searching for obscure facts without any guidance is frustrating for students and teaches them nothing about doing research. It becomes an exercise for Reference librarians to perform. Avoid telling students NOT to ask for help.
Libraries are complex institutions, each one a bit different from the next.
It is expected that students will need help, and library staff are trained to provide that help. Librarians cannot be expected to determine whether a given professor permits students to get help. Avoid arbitrary restrictions on sources students can use. This site is currently striving towards full ADA web compliance.