[pushkins]

Just gonna toss in my two cents worth to this post.

If your going to install drywall put the can lights in first, it is much easier than trying to fish wires in rafter spaces.
Install the can lights where they need to be, when your installing the drywall measure to the center of a can light and transpose that measurement to the drywall and put a mark (doesn't have to be exact) install the drywall but
DO NOT drive the drywall screws all the way in around the light fitting just put them in enough to help hold the drywall up (suggest hiring a panel lift from Home Depot it will save you heaps of time and trouble). when you have the screws all in get a roto zip and a drywall bit and using your general mark for the light start a small hole until you can see or feel the can light, then using the roto zip proceed to cut around the can light holding the zoto zip against the outside edge of the can light as a guide. You will notice that the drywall sheet will pull up into it's correct postition as your cutting the hole, when your done, drive in the remaining drywall screws

DONE....neat and easy !!!!!!! Same for outlet boxes and switches.