How to play the Albin Counter Gambit The Albin Counter Gambit starts 1. d4 d5 2. c4 e5 3. dxe5 d4, and there is a well known and beautiful trap with a pawn to knight promotion if white plays e3.  

Recently players such as Morozevich and Nakamura have been playing the Counter Gambit at the highest levels, and I found this page which discusses things.

Essentially, I am looking for more discussion of the key ideas in the gambit.  How long should I try to hold onto the pawn on d4?  Where do I end up castling?  (I find occasionally I end up with some choice.)  Which squares and minor pieces are usually the most important?  I am looking for some abstract goals and ideas.  What kind of plan should one have in mind when playing this opening as black?
Czechoslovakian Master Karel Prucha formulated some correct principles on how to play the Albin Counter Gambit and published them in Ceskoslovensky Sach 9/1962:

1. The Albin is playable only if it is treated as a pure gambit. 
   Black should not try to regain the pawn by attacking White's e5-pawn, 
   but must continue in gambit style with ...f7-f6.

2. After that, Black must castle short. Long castling leads to mutual attacks where        
   White's extra pawn becomes a factor.

3. Black should keep the d4-pawn at any cost.

4. Black's Queen should be posted on d7 with the idea of exchanging of the 
   light-squared Bishops by ...Bh3 and enabling additional support for the 
   d4-pawn by ...Rad8.

5. It is best to place the dark-squared Bishop on c5, which means that if White plays
   a2-a3, then a7-a5 is necessary to stop White's advance b2-b4.