Start at the farthest area from the attic access and work your way back . In my case, I had a roof leak which got the insulation wet. Wet insulation will not have any air pockets to prevent the heat transfer , as well as mold growing.

Start pulling the up the old insulation and any debris and place in one of the plastic trash bags.

Plan ahead to determine how much you can get done within the time frame you have allowed to work. You will be hot and sweaty with all the protective gear and want to work as fast as possible.

If there is a lot of debris like dust, dirt, leaves or bird feathers, you may want to use a shop vacuum.
Start with a clean area before adding new insulation.