I enjoy road-trips more than any other kind of travels. Exploring the world by car offers a lot of freedom and flexibility. It is time-efficient and relatively cheap; especially if you can split the cost among few people. Having traveled by car on four continents, here is what I do to design a great road-trip.
Great destinations. Before going on a road-trip I search for major destinations that would excite me. Typically, these are national parks, beautiful sceneries, cities, or scientific sites. I look them up on Wikitravel. Other times, however, the road is my ultimate destination. For example, I enjoy driving on scenic roads in the mountains.
Cool detours. Besides visiting major destinations, I like doing detours to check out attractions that are more or less on the way. Some examples? Coal mines, waterfalls, factories, distilleries, bridges. Roadtrippers is a good website to look for inspirations.
Scenic roads and enjoyable cars. I do care about driving. I find driving more enjoyable on a twisty road than on a straight highway. Whenever possible, I try to pick a route that maximizes the fun factor of driving, i.e., it features many curves, change of elevation, and beautiful views. Analogically, picking a fun car vs a dull one makes a huge difference. Especially on a long trip. If weather permits, convertible is my choice (and lots of sunscreen :-) ).
Amount of driving. It totally depends on the group of people you are going with. If I am on my own, or with people who road-tripped with me in the past, we do a lot of driving. 10-15 hours a day is not uncommon. Of course, driving that much is very exhausting. We try to switch drivers every few hours. Recently, however, I figured out my optimal driving schedule: 1) start 9am, 2) do 8h of the actual driving, and 3) finish by 9pm. On one hand, it is enough to enjoy driving. On the other hand, I am not too tired and can still party.
Stops. Each stop is very time-costly. I try to minimize the number of stops. Typically, I stop every 2-3 hours to take a short brake, get some food, and maybe refuel. Short stops make the actual travel time more predictable. For example, if I am on the highway, I travel 100km/h on average (including stops and slow-downs). So, if I am going to a place that is 400km away, it takes me about 4 hours.
Accommodation. I almost never book accommodation in advance when doing a road-trip. Why? I simply do not know how far I will drive. Most of the time, I would book a hotel/motel/hostel on booking.com or Hostelworld 30-60 minutes before the planned arrival. I always check that the place has a free parking and 24h reception.
Food. When traveling solo, I eat burgers and snacks (some favorites include beef jerky, cheese, and chocolate bars). Eating these is very time efficient. If we have more people on board, we search for places with decent food.
The right people. Spending multiple hours in the same car with the wrong people is a huge bummer. It is best to travel with people who: 1) enjoy driving, 2) do not mind long driving days, 3) are flexible about the schedule, and 4) are, generally, happy and talkative. I, however, absolutely do not mind traveling on my own. It gives me the most flexibility and the road keeps me occupied.
Technology. Waze is my favorite app for navigation. Real time information about road hazards, the police, and speed traps is invaluable. If we travel in multiple cars, a set of walkie talkies is very handy. It helps with navigation and makes the trip more fun!