My tips for planning the perfect road trip are to follow these steps:
Decide where, in general, you intend to go! Maybe you have a single destination in mind, or maybe you have several in a similar area. Choose your destination or destinations.
Take a cursory look at how to get to your general destination(s). This will generate a preliminary route that you can tweak later. Maybe there will be some detours or stops along the way that you find along this preliminary route. Add those intermediate stops to your itinerary!
Determine the amount of time required to take your trip. From taking your first look at your preliminary route, you should have a rough idea now of how much driving this trip will entail. Plan for at least 50% of your waking hours to be spent sightseeing. Sightseeing is the main reason why you decide to go on any vacation in the first place. If you're a Roadgeek like me, you don't need any sightseeing to be done in a single location while stationary, because seeing the road is enjoyable enough to people like me. However, normal people do not function this way; therefore, if a vacation is taken with my family or anyone who is not also a Roadgeek, plan for a normal ratio of sightseeing to driving. That ratio should be at least 1 to 1, so the time elapsed driving the preliminary should be at least doubled to give you the amount of waking hours you will need on this trip. If you intend to spend eight hours per day actively engaging in the content of your trip, divide the total number of waking hours in your trip by eight to get the number of days you'll need to devote toward vacationing. If you think you can stretch your days out longer, perhaps because it's summer and you have more daylight, consider dividing by nine or ten hours. However, I do not recommend any single person driving for more than eight hours in one day.
Decide the amount of time you wish to devote to each sightseeing destination. These decisions are completely up to you. Keep in mind that if you spend more than a couple hours at a particular destination, you will need to access services in the area, including food, drinks, and bathroom facilities. For destinations that you visit on multiple days (very typical if you're exploring a city or national park, for example), you'll need to find lodging nearby.
Determine the start and end points of each day geographically. The start of day one is your home, and the endpoint of the last day is home as well. Or alternately, if you fly to a distant airport and rent a car, the start and end points of your route will be the car rental joint at the airport. Plan for about eight hours each day for engaging in either driving or sightseeing activities. The points on a map, marking the end of one day and the start of the next, will be points with lodging facilities.
This is the most important item on the whole list: PLAN FOR SELF-CARE! Vacations are for making memories, and you won't be making good memories if you are too distracted by hunger, thirst, fatigue, or sickness to enjoy the sights you are seeing! Structure each day to start decently early, but not horribly early; you want to make sure of the daylight that's provided to you, but you also don't want to ruin your chances at sleep. I plan to start engaging in activities or driving around 8:00 A.M. I usually plan for an hour-long lunch break, starting sometime around noon. I also plan a 15-minute break in mid-morning (around 10:00 A.M.) and another one in mid-afternoon (around 3:00 P.M.). This allows you a break to use the bathroom and possibly eat a snack if you're sightseeing; or, it allows you to stop, get gas, and use the bathroom if you're driving. This structure is great because it provides space for bathroom break about every two hours.
Use this structure to scope out gas stations for your mid-morning and mid-afternoon breaks, scope out restaurants for your lunch around noon, and scope out hotels for wherever you end up at the end of each day. Research your hotels, restaurants, and even gas stations in advance of your trip. You don't have to require yourself to commit to any particular hotel, restaurant, or gas station, when the time to go on your trip finally arrives. However, you might be surprised to find that the area you're traveling to is more desolate than you thought, and you don't want this surprise to occur to you when you've already put yourself in that desolate area. You don't want to suddenly find yourself unable to access the service you need, so I recommend looking them up in advance! I will create itineraries for each day that show a gas station for the mid-morning break, a restaurant for lunch, a gas station for the mid-afternoon break, and a hotel and dinner restaurant for the end of the day. And again, I don't HAVE to follow the itinerary exactly when the time for vacationing does come. However, I like the comfort of knowing I have a viable option confirmed for me in advance when I reach any of the critical points along my trip. Researching viable restaurants is especially for people like me who have food allergies (I need to know I'm not suffering from my dairy allergy when I'm on vacation!). If you fail to find an option for a gas station, restaurant, or accommodation when you're doing your research, you may need to adjust the start point or end point for the relevant day and adjacent days.
Be aware of hiccups along your trip that can cost you extra time. These things include going through airport security, rush hour traffic jams, ferry crossings, and national border crossings. Leave some fluff time in your itinerary for these things.
Figure out how much your intended trip is going to cost. Look at the costs of your mealtimes, hotel stays, fuel, and admission prices to sightseeing destinations. Perhaps set aside some additional money for souvenirs and other items that may surface as necessary or desirable purchases.
Make adjustments based on unexpected droughts in services, sudden steep prices you decide to avoid, or anything you change your mind about! Revise, rinse, and repeat until you have an itinerary that will give you a trip that is exciting, fun, and exhilarating, but also healthy and safe!
I'll post my planning maps for two different types of road trips. This first road trip shows a week-long summer trip to the Upper Peninsula of Michigan, plus Mackinac Island and Traverse City. This trip shows an example of a trip I would go on with other people (namely my wife in this case), and it includes a bunch of sightseeing and activities other than Routesnapping and driving. On this trip, my wife and I went hiking up to waterfalls, went kayaking, went biking around Mackinac Island, took a dip into Lake Huron, and toured around the wineries and breweries surrounding Traverse City. You can see that the portions of the trip involved driving had breaks at gas stations or restaurants at two-hour intervals.
Eat your normal number of meals per day. Having a consistent eating schedule can help you focus on the joys of traveling. You don't want to be distracted by hunger or unusual levels of blood sugar. You don't want your chances of making beautiful memories tainted by someone getting hangry.
Plan to get the recommended duration of sleep per night. Ending up underslept and fatigued is a concern especially if you are spending hours behind the wheel of a car.
Don't become too much of a stickler for obeying every detail of your planned itinerary. If you find a hotel on the fly that looks nicer and has a better rate, go for it. If you find a restaurant you'd rather visit while traveling, and you'd rather go there than to the one you originally found while researching the area, go for it. The research for different gas stations and restaurants was mainly to guarantee the existence of at least one viable option, preventing the deprivation of these services when you eventually need them.
If you happen upon a cool thing you want to experience as you're traveling, you are free to make these impulsive decisions to see new things on the spot. However, be aware of the consequences of adding time to your day taking some detour or checking some unforeseen thing out on the fly. If the new thing you squeeze into your day takes forty minutes to see, you will reach the end of your planned itinerary forty minutes later. That may be daylight you can't afford to lose, or it may lead you to starve yourself at the end of the day if you push your evening meal time forty minutes later.
Hotels might not have rooms available. I don't like to reserve hotel rooms at the hotel's front desk upon arrival. I like to make reservations in advance so I have a guaranteed room. The act of reserving a hotel room in advance means that reaching the hotel is a concrete part of your itinerary that you can't modify on the fly, which can cause feelings of rigidity and entrapment into your itinerary; however, I think it's worth it to guarantee yourself a room somewhere. It can happen, where all of the hotel rooms in an area are booked due to some important local event. The freedom of knowing you have a bed to sleep in at night is more important than the freedom to deviate from your itinerary, in my opinion.
Don't overextend yourself. Don't create a situation where you're driving for too long of a period. When on my own, I try not to drive a route that takes more than 6 to 8 hours to drive. If you're taking turns driving with at least one other person, you may be able to make it doing 10-12 hours of driving in a day.