I have been stuck on this one for a long time.
At first I didnt have a proper multimeter. Mine is on permanent loan to somebody somewhere... So I ordered one from China. 3 months and 2 weeks later, I get it. I go to set the current limits and...
Wow. So much, I learned.
On the Vicious1 site, there is a handy video from Pololu, most of which I didn't understand. There is also some words, some of which I kind of understood.
The procedure seems straight forward - ground here, tune pot there, bingo! Some issues I ran into:
Do I power the driver on the ramps board to set the current limit? Do I buy a pololu board and try that? Do I need the motor connected? And does the current limit need to be different than mentioned on the video because I am running two motors from one driver?
Solution: I ended up throwing the driver on an empty breadboard and wiring (with a little guesswork) from a still of the Pololu video, no ramps board, no motor, just power. I will get a Fritzing up here ASAP. I needed 5.5v and 12v.