I found a nice table on how many delegates are assigned to each state, along with where those delegates come from. For the superdelegates, there were four subcatagories, Governor, Senator, Representative, and State Party Leader. That makes sense. But what is the process behind selecting specific individuals out of the last three groups? Who decides who is chosen and who is left out?
This article discusses in in the context of the 2008 democratic primary. The short form is that there is no "choosing" involved. If you got that impression from your table, it misled you.
Instead, people are either a superdelegate or not, based on their current or previous jobs.
Every Democratic member of the House and Senate, every Democratic governor and members of the Democratic National Committee (such as state party chairs, vice chairs and national committeemen and women) automatically get to be superdelegates. Also included: former Democratic presidents and vice presidents, former Democratic House and Senate leaders, and ex-DNC chairs.
There is no fixed number for superdelegates. Anyone who qualifies by the convention is in, and anyone who used to qualify but no longer does is out, and that may make the numbers change. For example:
The Democrats picked up a superdelegate when they won the congressional seat of former Republican House Speaker Dennis Hastert in a special election in Illinois in March . They lost one with the death of Rep. Tom Lantos of California. But they will regain that superdelegate if former state Sen. Jackie Speier, who is heavily favored, wins the special election to fill the remainder of Lantos' term. And so on.