What determines the orientation of a coupling/blocking capacitor in an amplifier circuit?
Depends on the DC level of both sides: If one side is higher then (+) terminal should be connected to that point.

Let's examine this on the example circuits shown in your question:

1) At point A, DC level is 0V. At point B, DC level is \$V_B = 12 \cdot 10/91 = 1.32VDC\$, so (+) terminal of the cap should be connected to B.

2) At the point on the left side (i.e. input side), there is no DC level shown, so we'll suppose it 0V. At the point on the right side, DC level is \$V_x=24\cdot 10/20 = 12VDC\$, so (+) terminal should be connected to the junction of R2 and R4.

3) The coupling cap at the input is not an electrolytic. So there's no polarity. Likewise, output coupling cap is not an electrolytic as well. But if it was an electrolytic, since the DC level at the output (i.e. at the junction of RC and output transistor's collector) is non-zero then (+) terminal should have been connected to that point.

hth.