If you don't have a lazy $1000 to drop on Argo Navis, you can make a surprisingly good system for about $50. You print a 360 degree circle for the base of the dob which tells you the Az in degrees, and use an angle gauge on the scope tube to get the Alt in degrees. Then lookup the current coordinates of the object you want to find on a device (laptop with stellarium, phone with Skeye or ipad with sky safari etc.) and point the scope to the coordinates.
It is genius in its simplicity, more info here:
http://www.cloudynights.com/ubbarchi.../o/all/fpart/1
The early iterations use a printed angle for the Alt as well, but then someone had the idea of using one of these ...
http://www.amazon.com/Wixey-WR300-Di.../dp/B001PTGBRQ.