If you're going away for more than a couple of days, it's a good idea to designate a person at home as your point of contact. This allows you to streamline the flow of information you might need to give others while you're gone; it also gives someone at home a way to reach you if something arises while you're gone. Staying in regular contact ensures that someone knows you're okay -- or, if you fail to make contact at an appointed time, it assures that someone will be alerted. Depending on how vigilant you'd like to be, plan specific contact days (and possibly even times) for checking in. Supply your contact with an itinerary, and highlight the days you plan to get in touch. If you change or update your itinerary, let your contact know. With each phone call, set up a day and time for your next check-in.
If you have a cell phone, bring it -- as well as any phone numbers you think you might need. This kind of forethought does not necessarily mean that you will always be close enough to a cell tower to place or receive calls. If your trip is taking you to the hinterlands, arrange to check in with your contact when you are passing through a populated area that is bound to have adequate cell coverage, or stop at a pay phone. If you don't have a cell phone but have been waiting for a reason to get one, now might be the time. If you are not ready to commit to a yearly service contract or you don't really need a cell phone when you're at home, consider a prepaid cellular phone, which you can purchase at consumer-electronics stores. The phones come prepaid with a set number of minutes; you can buy cell phone cards that allow you to add minutes, as well. They might cost more per minute than a standard cell phone, but you only pay for the minutes you use; there is no monthly service charge.
If you are simply not the cell-phone type and prefer to rely on land-line phones, make sure you purchase a phone card for your trip. That way, you can borrow a phone without having to make a collect call or impose on a stranger's generosity. Or, you can find a pay phone and pay a slightly higher per-minute rate on your phone card. Many campgrounds allow long-distance calls only with the use of a phone card, so the card is sure to come in handy on your RV trip. Whatever minute limit you purchase, many phone cards allow you to add time simply by choosing this option and billing it to a credit card when you call the toll-free number on the card.