Can someone describe a good/easy mental procedure to choose the best move here? This is kind of like magic to me. Once they show you it becomes obvious :) :(

Can someone point out a good/easy strategy that a player can mentally train/use to decide what is the best move here for black?

Note: Guys, there is a best move for black there can lead to a checkmate later. The goal is not to find it, but to come up with a procedure to find it so it can be applied to other positions.
I would say there are two tactical possibilities for black here:


1…Bxd3 2.Rxd3 Rxa4 3.Qxa4 Nxb2 wins the pawn back with a better position (the a3 pawn is now weak).
1…Rxe3 2.fe Nxe3 3.Qe2/d2 Bxd4 and the a4 Knight is hanging and the d1 rook is hanging with check … it still isn't over, in a game you should probably calculate further, but I'm to lazy to do that now.


There actually is an easy rule to find both of these tactical strikes:

Consider all captures!

Usually this rule is even broader: Consider all forcing moves! This includes captures, checks and attacks on stronger pieces.

Disclaimer: As with all rules this maxim has to be tempered by experience.