On the 06 the high idle was an option, your dealer has to program it, mine will go from 725 rpm to just about 1000 rpm by its self if its cold enough, I don't have the cruise option for high idle, I have never plugged my truck in and I live just below the southern tip of Alaska, they fire up pretty well as long as the batteries are good.

 

may not be right, but this is what I do..

turn key, wait for LP to stop buzzing, and truck to stop chiming, start the truck (usually fires up really quickly) let it idle a few seconds, turn on AC to where I want it.. and let oil pressure go up to where it needs to be and sit there for a minute or two, then up and at em...

in the wintertime, it don't get too cold down here, so I high idle it for a few mins if its below 40 degrees, but I don't change the procedure to start it.. and then I go...

 

The high idle w cruise feature has to be activated by the dlr or a programmer and stick shifts require a jumper wire installed. Been a while, forget the details but a search here will plumb you up.
Auto high idle only activates at low temps, below 20 or 10 deg or something.
These trucks start well in the cold. I'd plug it in to help with quicker warm up below freezing but not necessary for the truck to star easily. 3rd gens, mine anyway has started in any weather down to -20 without plugged in but would really recommend plugging in if it's getting close to 0.

 

I plug in a freezing or below. Don't worry about warming up the truck too much down here. I start, let it idle for just a minute and go. I will use High idle if it is cold out and I forgot to plug it in. Works wonders for defrosting windows.

 

I live in an area where it gets super cold during winter. -30 wind chill is easy to see.

When its really cold I cycle glo plugs twice. Always run power service. And I plug it in if I know its going to get below 15ish

Let it warm up oh 10 minutes on average. And drive it easy till all temps are reached to a normal.

 

That is what I do and I also use Mobil Delvac 0-40 full synthetic.
Jim O

 

I've been super impressed with my '06.
I've run both Rotella 15w-40 and Rotella t-6 5w40 in the winter.
In temps down to 15 below, i just wait for the WTS light to go off and she fires right up. I give it a minute just so I know oil has gotten everywhere and away we go. It takes forever to build heat idling so I drive it easy rather than let it idle. No fuss, no muss, no plug in.
My brother's 7.3 powerstroke on the other hand.....