Using the Tools of the Trade
With all the technology readily available today, staying in touch is simple.  If you plan to only check voicemail, send a quick email to all contacts in order to tell them while you are away you will not be utilizing email.  If you will only be checking your email and not your voicemail, leave a polite message on your voicemail stating so.  It is also important to have a reliable colleague be an emergency contact for those clients who may have urgent needs.
Checking In
While on your vacation you can not be running to your lap top every hour on the hour in order to check messages.  Choose a time of day to check your emails or voicemail and inform the office when that will be so that they may get important info to you and know when you will be receiving it.  Noon seems to work best; if any emergencies have reared their ugly heads, you will have plenty of time to contact the key players in order to get it resolved.
These few rules of thumb could make all the difference in enjoying the time you have away from the office and when you return you won't skip a beat!