Hi there,
I hoping if u could spare a couple minutes to help me out with a couple questions.

my 1st Q is...
I have an attached garage that has been drywalled about 1 ft from base to top of wall; although, i've noticed they did not place any insulation behind. i am not planing to heat my garage, but only wish to keep the temperatures from reaching the extrems. Should i rip off the old drywall, insulate, and refinish to the floor? Also, should i place insulation under the roof btwn the 2 1/2 ft joists and stapple a screening to hold it up? furthermore, do i stuff insulation in the pockets where the wall and the roof intersect to prevent air coming from outside?

my 2nd Q is this.
I am also insulating my basement. The walls were simple, but I need help with the basement ceiling. it seems easy to place fibreglass insulation btwn the empty ceiling joists, but how do i handle the ducts and water pipes. should i cut the insulation to fit on either side of the ducts or wrap the ducts and pipes with thermal insulation?

thanks for reading.
hopefully, u can clear up some or all my questions.

In joist area you would probably need to install a ceiling with insulation to prevent the transfer of heat. the air entering from the soffits is designed to both cool the roof and prevent ice build by having different temperatures outside to inside. In regards to the walls. some companies will inject insulation into the walls however if there is and bracing or conduit or anything that can prevent it from landing perfectly there will be gaps.
But it is much better than no insulation, here is a video:
http://www.bobvila.com/BVTV/HomeAgain/Video-1220-04-0.html

In the basement take a look here: to see the blown in insulation between the joists.
http://www.bobvila.com/HomeAgainExtras/BIBCA/index.html

I personally wrap any pipes including those for HVAC lines to prevent condensation.