Vacuum Advance Adjustment Help

Fellow FABO's, I have a 440 RR and when cruizing down the road, the car flutters and spits and back fires a little. A friend said that the vacuum advance needed adjusted. Sure enough I un hosed the vacuum advance and it was my problem. Which way do you go with the adj screw in the vacuum nozell? Out or in to lessen the vacuum. And is there a procedure to this or just hit and miss? Thanks for any tech talk info.