Buy the insulation pre cut to the width between your joists and make sure it is a minimum of 100mm thick.
Rig up an inspection lamp so you can see what you are doing.
Buy some 1" thick board that spans the joists so you can kneel or stand.
Tuck the new insulation neatly between the joists.
Lag the top and sides of any water tanks.
Dont tuck the insulation into the soffit space - the roof needs to breathe.
Don't cover any pod lamp fittings with insulation.
Wear a dust mask.
Don't insulate the rafters going up to the roof ridge - concentrate on the ceiling tops.
Finish off by having a shower and turning the heating OFF.
John
September 2009