Really, you could start by just picking up a Lonely Planet and looking at the suggested itineraries they offer in SE Asia books. With 3 months you could see a lot of Vietnam, Cambodia and Laos. Depending on the time of year would make for adjustments for different rainy seasons in Vietnam probably - but there is a very basic loops you could set up. I'd usually fly into and out of the same airport for the cheapest possible ticket, so if you started with HCMC you could work your way up Vietnam, then over into Laos and then down Laos and through Cambodia, or reverse that or start with Hanoi. A pretty basic loop that you can speed up or slow down on as you like and you won't have to take any other flights.
So I am planning a 3 month trip to SE Asia early next year. I am basically looking for a "cookie cutter" itinerary that excludes Thailand, only because I was there last year (loved it, want to see others). By cookie cutter I mean - hitting the main stops/cities before entering/exiting each country. I am open to all (Vietnam, Cambodia, Laos, Burma, Malaysia, Indonesia, Philippines, etc.) and all forms of travel (flying, ground, boat). I fully realize that I will not hit each of countries I listed (3 would be ideal, 4 if lucky) - and I definitely do not want to rush this. That's what the rest of my life is for..
All advice is very much appreciated!
Thanks caseyp. I'm aware of the itineraries in the Lonely Planet books. My in-depth itinerary per region will begin when I figure out my basic loop, as you put it. Vietnam -> Laos -> Cambodia -> Vietnam sounds intriguing.