well... when it is -4000 outside I usually have to wait 10-20 minutes just for it to start warming up, but right now I wait till the needle starts moving then I keep it under 4k until it hits the dot on the temp gauge.
Not letting it warm up will kill your gas mileage if you only drive short distances. I got a record low 14mpg in my g20 last week because I was commuting barely over a mile and it was like 10 degrees out. Took it on the highway over the weekend and its back up to 29mpg. I thought something was messed up for sure but nope, just the cold engine wasting gas.
I usually let it warm for maybe 5mins, or until the temp guage is at normal operating temp. My car drives like **** if it isnt warmed up because of the cams. I usually turn it on and let is sit, do something in the house and wait for awhile. When im at work, I go outside, start it, and lock it with the alarm, and take the remote with me leaving the key. I need remote start.
When my car was drivable, I'd wait for the needle to get just a little above C before starting to roll it, no matter how long it took. Stomping began right when the needle would reside in the middle of C and H.
I wait until the water temp reaches 100* F before moving. After that...I can literally feel the Redline Heavy Shockproof thin out in the tranny. Until it is nice and warm (2-3 miles, minimum), I take it very easy on the tranny.