In my own silly opinion (I agree with Jason) it's not the greatest way to go (soldering the shield to the plate) if it floats your boat then go for it!! (ha, ha).
 
I think it's better to solder the shield to the input jack. It's also nice to ground the input jack to the same spot where the cathode resistor (on the 1st stage) is grounded (again, in my opinion). For the most part (when building amps) I like to run a ground wire from the controls to the input jack(s) and then on to the preamps ground points (if anyone can follow that--ha, ha) then naturally to ground. It seems to keep the amp pretty quite. 
 
I use 18ga solid core wire for this....
 
1.) I usually run one peice across the control pots and only for the controls that are actually grounded (IE: Midrange, preamp volumes, master volume etc.) 
 
2.) From there I run the wire to the input jack(s)
 
3.) From the input jack(s) I run the wire to the board that contains the preamp's circuitry. 
 
4.) At the furthest edge of the board (the side closest to the control pots) I run the wire along the edge of the board. Any ground points are connected to this (IE: voltage dividers, cathodes, grids, etc., etc.)
 
It keeps clean amps noise free when cranked hard and it keeps high gain amps noise free as well. Of course proper layout and lead dress also help!!! (ha, ha) 
 
As a side note for cathode biased amps (I'm going off from memory here) if you ground the bias splitters to the same ground point as the cathode resistor/cap that also eliminates a great deal of hum. The same ground concept can also be applied to the power amp section as well. 
 
I hope this helps
Trace
Voodoo Amps