Bias adjustment procedure

[voxworld]

Can anyone guide me through setting the bias on a JCM2000 DSL50 head?
It has three contact prongs with an anjustable pot on either side.
The amp is a 1997.
Any suggestions on bias settings would be great as well.
It currently has a pair of Svet EL34's and four chinese Marshall labeled 12AX7's. Not sure how old these are, I just picked the amp up today, thanks in advance, vox.