How was the slave trade organized and who controlled each aspect of the trade?

The Atlantic slave trade was taking place between Africa
and the Americas, for the most part.  Of course, different people participated in it at
different times and different people profited from it.

In
general, the slave ships tended to be English.  They could be from England or they could
be from the Northern colonies of North America (Massachusetts, etc).  These traders
profited a great deal from taking the slaves to the Americas and from shipping American
goods such as rum to England.  Profits were also made by people who outfitted the ships
and the people who wrote insurance policies for them.  In other words, many people in
the North profited.

It is also worth noting that some
Africans profited.  Specifically, the Africans who caught other Africans and sold them
to the slave traders made a great deal of profit from their part in the
trade.