Some good suggestions from capybara there.
I make an announcement in the first class about email etiquette. I make clear to the students that i am not their text buddy, that emails need to include a decent salutation and need to be signed at the end, and that the subject line should convey the subject of the email and not just “Hey” or “Class.” In turn, i show students the same consideration when i send emails to them. I also let them know that, while i make an effort to respond to emails as quickly as possible, this does NOT mean that i am available 24 hours a day, and that any student who finishes an email message with “Please get back to me as soon as possible” will likely go straight to the back of my email “To do” list.
I think learning to allocate your time between emails and office hours is essential. If it takes me 15 minutes of typing to explain something, i can probably explain it directly to the student in about 5 minutes, with grater clarity and with the opportunity to make sure he or she understands it properly. For that reason, any email asking about significant matters of content will be answered with a promise to address the issue in class (if i think it’s something that would benefit everyone), or a request to attend office hours.
Also, i’m a strong believer that, if the question is about something they should already know or be able to find out easily for themselves, there’s nothing wrong with telling them so, sometimes rather tersely. For example, if a student emails me to ask when the next paper is due, or what reading they need to do for the upcoming class, my response (cut and pasted from a small series of stock responses that i keep on hand) will be:
If you enable the lazy ones by answering all of the most mundane queries, they will never stop. Like capybara, i try to be careful not to send out snarky emails, and will often give myself time to cool off if i think the message i’ve composed is too harsh, but i also think you need to make it clear that you’re not at the students’ beck and call for stuff that they should be able to work out for themselves.
Having a Blackboard page or some similar type of course site to post announcements and other information is very handy, and if you keep it up to date and tell the students to check it regularly, you can save yourself considerable email hassle.