This will cover the unit pictured below. The first trick is to get the locking nuts off.  They have a small "blob" of epoxy on them under the paint.  The easiest way to break them free is to use a 3/8" deep socket and simply unscrew them.  Take the nut and rods completely out and use a pair of dykes to break loose the epoxy.  Then grab the rod above the nut, so as not to damage the threads under the nut, with a strong pair of pliers and screw the nut DOWN each rod about 1/4".  Do NOT try to break the rod free of the nut by using a screwdriver in the slot at the top of the rod!  It WILL break!  Once the nut is loose, you can thread the rod and nut back in the duplexer and then use a screwdriver for tuning.
The pass part of the duplexer is about 35MHz wide, so if there are any cell towers near, you will have to use an extra filter on the receiver. 
The goal here is not to have the best looking frequency response, but to get the best IL on the pass freq. and best rejection on the notch freq.  I have found that tuning for the pass freq about 10MHz up from the edge of the bandpass on the notch side yields the best results (See sweep photos below).  When tuning the pass adjustments, make sure the notch adjustments are well out of the passband by screwing all the RX side notch adjustments OUT about 1/2" from where they were before you started and the TX side notch adjustments in to where they were originally.  Adjust your PASS first, then the NOTCH.  Go back between them a couple of times until you are satisfied with the results.  Below are some diagrams of what each adjustment does.
As you can see by the paint marks, most of the "affecting" screws are up about 1/4" from where they were originally.  The notch adjustments are VERY TOUCHY!  When doing a final tune, the locking nuts should be pretty tight, because tightening them even a little will affect the notch quite a bit!  Also, the notch "fine tune" adjustments will also affect the depth of the notch somewhat.  If your notch isn't deep enough, try moving both fine tune screws a couple turns in the same direction and readjust the coarse tune adjustment and see if it gets deeper.  If not, try the other direction.
I have screwed myself up several times on these by not making sure that the RX side had no affect on the TX side before trying to tune the TX!  Had to go back and completely mistune the RX side, then retune the TX side.  Same goes in reverse!  These things can be a bitch if you are not careful!  You CANNOT tune this with just a wattmeter!!!  You need a good analyzer like an HP 8920 with a tracking generator!
Below are the TX and RX sweeps after tuning.  Not pretty, but very functional at the desired frequencies!  Both notches were about 100db and both pass insertion losses were less than 1db!
The arrows are on the respective pass and notch freq's.  The overall shape is terrible, but remember, we're only trying for one pass and one notch freq, not the whole band!