Having all the tools in one place and within easy reach is half the battle for any project.
Razor Knife: To cut the fiberglass insulation , you will need plenty of replacement blades as the glass will dull the blades very fast.
Dust Mask: You need to protect your lungs from the fiberglass fibers that will become airborne as you cut and move the insulation in place. Read the information on the package to make sure you are getting the mask for the intended hazard.
Safety Glasses; You will need eye protection from the fiberglass fibers and any debris you pull out when cleaning the space. Use an oversized pair over your prescription eyewear.
Gloves: A pair of cotton gloves will protect your hands from the fibers and will soak up any sweat in your hands. Keep a couple of pairs handy when the first pair gets too wet.
Hard Hat: Protect your head from the roof rafters. You will be surprised on how many times you will be banging you head and will be thankful for the protection.
Paper Bodysuit: In my case, I was working in a tight space and was exposed to a huge bird's nest that created nasty debris along with the fiberglass fibers. It is easier to cleanup once the job is done.
Plastic Trash Bags: Use a heavy weight trash bag to dispose of the old insulation and any debris. I made sure that I placed in old insulation in the bag before leaving the attic.
Insulation Battens: Plan on buying 10% more than the maximum square footage you are replacing. You do not want to have to stop and run back to the store if you run short.
Ladder: Plan on using a ladder that is tall enough to allow you access to the attic. Be careful not to kick the ladder over as you move into the enclosed attic crawl space.