you have to make sure the steam is off on your iron and don't even have water in the tank.
then you have to lay the iron down and leave it there for a few seconds, do not move it around, then lift it up and place it down again in the next location, do not move it around, try to make a little overlap between pressing sections that way you adhere all the sections.
if you're working with thin or difficult fabrics (silk, t shirt, etc) use the fuse a shade first then put the fleece down.