Carb Tuning

Well here we go again.  I've got the carbs all rebuilt, but I can't seem to 
get them tuned right.  It's idling way to high even if the are the screws all 
the way out, same problem as before I rebuilt.  Suggestions?  
And how can I set the mixture?  I know what does what, but how do I get it 
just right?  I've got a unisyn and all that stuff.  

Thanks
Matt Smith
'67 Sprite