To plan a perfect road trip, you'll need four things; company, transport, a relaxed state of mind, and a destination.
When it comes to company, most of us have two options, friends and family, the former being the better choice when it comes to this. Family are always fun to have around, in most situations, but when it comes to hitting the road and having a blast, friends are the clear option.
Transport would be the biggest problem in road tripping. Taking your own car could be a hassle, so you'd resort to public transport. Busses and trains are real fun, and offer a challenge and unique joy to the trip. Although using the trains' pubic bathrooms and sharing a cabin with sweaty little men may not appeal to most people, you have next to no stress about petrol, maintenance, or loosing your keys at a hotel. Then again, nothing beats high speed getaways down NH4 with friends in an A/C car! So here, private cars are the best.
A relaxed state of mind is quite easy to attain. You just need to let go of all work, deadlines, and anything that might cloud your mind. On this note, throwing your phones out of the car might be a good idea!
And last but certainly not the least, the destination. It goes without saying the you need to plan a spot which is far away from home. Not too far, but far enough that your mom can't reach you even when you're in trouble. That said, beaches, resorts with swimming pools, and hill stations might be a good idea. Even wandering aimlessly in a car can be extremely fun and adventurous.
Overall, according to me, the Perfect Road Trip is one where you have all your best friends, in your car, leisurely cruising down from Chennai to Kanyakumari and back. The souvenirs should be nothing but the memories, Hangover style!