Once you've got the calipers out of the way, the rotors are loose on the hubs, except for a single phillips-head screw. Depending on your location in the US, this screw can be difficult to extract due to corrosion - treat it with some PB Blaster or other penetrating oil prior to removal. If it's stubborn, try using an OLD phillips screwdriver and a hammer. Put the screwdriver in the slots of the screw, and while turning to remove (to the left), whack the end of the screwdriver with the hammer. If the screw is stubborn, have someone step on the brakes to hold the disk in position first. Loosen this screw BEFORE removing the calipers.

Calipers (at least the front ones) are a multi-piston design with pistons on both sides of the disk, so be sure which bolts to remove - I screwed up and removed he bolts that separate the halves of the calipers - big mess requiring a re-bleed of the front brakes.

Once you've got the retaining bolts loose for the calipers, you may need a pry bar to work the pistons back into the calipers so they can be slid off the disks - just pry gently against the pad backing plate (where the friction material is bonded) - you can crack the bleeder screw to make this process easier, but you risk introducing air if things don't go exactly right.

Be SURE to not let the calipers hang from the brake hose once removed - use a wire coat hanger or stout bungee cord to suspend it.