Calculate the amount and type of insulation needed, seal all air leaks, install rafter vents, use plastic sheeting and plywood to prepare the area and blow the insulation to the appropriate level are the steps for blowing insulation into an attic. Always use the appropriate safety and respiratory equipment when blowing insulation. You can typically rent the equipment needed for the task at most home supply stores.
Blown-in cellulose insulation calculators are available from many home improvement stores such as Lowe's and The Home Depot. The calculator tells you the correct amount and type of insulation that you need based on the size of the attic and the climate zone where the house is located.
Locate any open areas around vent pipes or other air leaks and seal them with the appropriated caulk. Lay down plywood sheets to allow for a safe temporary walkway to work areas. Install rafter vents over any soffit vents or complete any needed repairs to previously installed rafter vents.
Install polyethylene sheeting between all of the rafters, making sure it remains at least 3 inches away from any heat producing devices such as chimneys, flues or recessed lighting before stapling it in place.
Load the blowing machine and carefully blow the attic full to the desired level working your way backward from the outside to avoid compressing the new insulation as much as possible. Take care not to step off of the plywood walkways and through the roof.