My method of banking and kicking (for 1 rail shots) is the 2 to 1 method. Its explained in this:
It is step 3 in the video.
But the same thing works for banking. I will find the closest natural 2 to 1 line (as if i was kicking the object ball into the desired pocket). If the ball is on the natural line then I use this line. If the ball is not on the line then I need to adjust. I find the closest natural line and see how far left/right of the line the ball is. If the object ball is 4 inches left of the natural line (from center of line to center of ball) then I want to adjust 2 inches left on the rail with my aim. So why 2 inches? The system is 2 to 1, and whatever distance we go on the 1st rail we only go 1/2 the distance on the 2nd rail.
The keys to all banking:
Speed - what speed is natural table speed for that table? Firm speed shortens the bank
Spin - NO spin on the cue ball
Aiming - if you are off an inch on your aim you will miss by 2 inches at the pocket
Collision Induced Throw - if you are shooting a cut shot for the bank, the object ball will not go exactly where you are aiming due to CIT. AND it will pick up a little spin. If you are cutting across the line (cue ball going towards the shot line - crossover bank) the shot will naturally want to go long/wide. If you are cutting away from the shot line (cue ball going away from the shot line) the shot will naturally want to go short.
Most players would just use a little spin to counter act the CIT but then you are also getting spin that you need to adjust for.
What do you do if the bank is not anywhere close to one of the natural 2 to 1 lines? You can use spot on the wall for 1 rail banks/kicks. Going from one corner pocket - through 2nd diamond on opposite short rail - to intended corner pocket. You aim through that 2nd diamond and find a spot - something 12-15 feet past the table. Use this reference as your new aim point.