If you are starting gfo because your phosphates are higher than you want you can start by adding 1/2 the recommended dose. This helps to have a gradual reduction, as some have reported corals being "shocked" by a rapid change in phosphate levels.
The only other gfo tips I have are rinse it well, keep the flow low so the surface is just moving, and put the outlet on a chunk of filter floss for a couple hours/overnight after you change it (helps catch fines and/or gunk from the hose that is dislodged from cleaning).
Hth,
- Ian