Best bet for Decolonization to work better is to start early, planning out the colonies to be more than markets for the home nation's goods and resources colonies. That means either a major growth in the number of colonists to set up a base of skilled people in the nation (this has the potential to backfire - see Rhodesia and Portugal's African wars), training locals in substantial numbers to be those skilled people (a major problem in Africa and India owing to the latest racism that remained for decades among the colonists) or both.
Keeping nations unified is also IMO a very good idea, especially in Africa. Bloody near all of Africa's ugliest conflicts have been based in whole or in part on tribal loyalties, and yet the places where the biggest number of tribes exist in one nation (Kenya, Tanzania, South Africa) have had far less of this. (Angola and Mozambique also sorta qualify - the wars there were in large part proxy wars between the USSR and Cuba on one side and the United States and South Africa on the other.) Nigeria is the primary exception to this, but Nigeria was also a proxy fight backed by oil interests. India's decolonialization has left one prosperous nation (India), one impoverished, hopeless craphole (Bangladesh), one civil war torn, bitterly-divided nation (Sri Lanka) and one nation run by its armed forces and infested with violent Muslim fundamentalists (Pakistan). It should have never been divided, if you ask me.
Best way to start this is for Europe to have the realization after WWI that colonialization will inevitably fail unless the benefits of it go to all of the colonies' subjects, and so begin the process of developing the colonies in the 1920s. This also has the effect of getting the anti-colonialist Americans off everyone's backs to a certain extent. Thus, the 1920s wealth is also shared with many of the colonies, with the resource-rich colonies and the jewels getting first pick of the new wealth. The Great Depression causes this point to be hammered home further, and in the cases of both Britain and France several million people from the homeland go to the colonies in search of a better life, which in many cases they find. After WWII, they make the job of economic growth easier, and the colonial powers begin steering the nations towards independence. India is first off, becoming independent in 1949, with the African and Asian nations following through the 1950s, 60s and 70s. Western Europe and the United States battle hard to keep these nations within their spheres, while still allowing them to make their own destinies.