Books
The Milepost has to be on the top of everyones list. This is a detailed listing of every place of possible interest along every possible highway you may travel on your trip. It tells you by mile or kilometer from the various junctions the location of everything from fuel stops to turnouts. We found it to be quite accurate on road conditions and areas of road construction. The new version usually is published in March.
Travellers Guide to Alaskan Camping - Mike and Terry Church have compiled a detailed guide to the campgrounds of Alaska organized by highway. We used this book as much as the Milepost.
The Great Alaskan Tour Saver - This book cost $100 and has over 150 coupons for discounts, two for one fares on tours and even some free items (do get the free fudge in Tok). It will pay for itself many times over. Just the flight over Mount McKinley saved us $250.
Maps
A good set of paper maps. We use AAA for our maps, and have completely worn out our Alaska and northwest Canada map this trip. Maps make it much easier to put the distances into perspective and to see the relationships between the places you visit.
We have used a GPS and Street Atlas for navigation for many years. Until the 2007 edition, Street Atlas did not have street detail in Canada but it does have the major highways, so we mostly used Streets and Trips while there and Street Atlas in Alaska. Whatever your favorite mapping program, used with a GPS it will be a big help in navigating the roads in Canada and Alaska and in finding your way around the larger towns and cities. We also use a Street Pilot and that can be used instead of, or in addition to, a mapping program. A GPS that can be moved to the car (if you're travelling in a motorhome) is a big advantage here.
Hookups
You won't find too many campgrounds with 50A service. Most have 30A and some have only 20A. We were always able to find 30A electric and water, and full hookups are available in some campgrounds. All have dump stations so lack of a sewer connection isn't a concern. The Travellers Guide to Alaskan Camping will tell you all the details on each campground.
Fuel
We found diesel fuel easy to find. As most everything up here, the prices are higher than we're used to, avaraging close to $4.00/gallon in Canada this summer. If there is more than one fuel outlet do some comparison shopping, you may save a bit. Some Canadian outlets will give a $.03-.05/liter credit for purchases of 100 liters or more. We tried to drive on the top half of the tank as it can be a ways between fuel stops in some areas.
Miscellaneous items
Insect repellent. We took four cans of Deep Woods Off with us and rarely used it. The Alaska summer of 2006 was cool and wet and bugs were not a big problem. However, if you do any hiking in the woods, as some of the tours include, you will find this helpful. Get some with a high percentage of Deet for the most effective.
General comments
Keep a log. We found the trip logs of those that went before us to be invaluable in planning our trip. A public record of your trip is a very nice thing to do so your family and friends can follow along on your adventure. Some post their experiences on our forum while others create a web site for the purpose. We chose the latter so our non-RVing friends and family could read about our journey and see the numerous photos we've taken, all in one place. A log can also be as simple as a series of emails you send to family and friends as you travel. Do record your impressions of places and your expenses, these are very helpful as planning guides for others.
Be flexible and take your time, this is not a trip to take on a set schedule. If you're enjoying an area, stay longer. At Denali, you may have to wait several days for nice weather to take one of the bus tours or particularly a plane ride over Mount McKinley. The latter is definitely worth the money if you can get a clear day. We were fortunate to get such a day right after we arrived, and didn't see another one the rest of the week we spent there. The same applies to the many boat tours that are available in Alaska.
Keep your camera ready, you never know when a moose or bear will appear. If you see several vehicles stopped on the road, it's probably for some wildlife photos.