Destination & Duration
Your destination is a key part of your planning, and no doubt it is also what inspired you to go on a road trip in the first place. Will you focus on one American state? Do you want to tour the British Isles? How about a European road trip (that gives you SO many options), or do you want to go all out and travel around the world? As far duration goes it sounds like an obvious thing to plan, but working out how long your going for will enable you to work out your destination, and (if you're planning to do several countries) how many countries you'll realistically be able to visit in that time. On one trip, I travelled through Spain; Portugal and France, but spent a week in Portugal so I didn't feel like I was rushing from one place to the other. That is key - make sure it's a road 'trip', not merely a long drive from place to place.
Finances are a crucial part of any holiday; but on a road trip this will determine exactly what sort of accomodation you'll be able to stay in, and what trips you can do along the way. Are you limited to camping, or can you stay in a few budget options to enable you splash out at some stage of your trip? I can HIGHLY recommend doing this, as you feel like you're spoiling yourself! I stayed in a few cheap places, and then stayed in the most stunning former convent as a reward. I always think you can budget for your accommodation costs before you travel, and then estimate your spending money ensuring you won't run out!
While a road trip is all about feeling free to go where you want, and stay longer in one place if you really like it, I believe it's important to have a good itinerary to ensure you're not travelling too much in any one day. I found that six hours really is the limit in a car if you're in a hot country - after that; you stop enjoying the scenery; want to get out to stretch your legs....and have a cold drink! One of the interesting things I did for a couple of my destinations was not pre-booking any accomodation. On reflection although it was nice to fee free to arrive in a place and have a drive around to see where I wanted to stay, it turned out to be the most stressful part of the journey. Interestingly, the places I stayed in were also more expensive than the ones I had booked before I travelled; but I settled for them because I was tired and just wanted to drop my bags, and explore.
So those are my tips for planning a successful road trip. In my experience they can be the best holidays as you discover places that are totally off the tourist trail, as you're not restricted to flying into a specific airport. Some of the places I visited in Spain were full of locals, and five hours from the nearest airport - those can be the little gems that you just wouldn't get on your average holiday. If you're thinking of going on a road trip, DO IT! Embrace the planning; surround yourself by maps to organise your travel, and when you're there enjoy the trip of a lifetime away from the regular tourist trails!