Watch how you can create the proper rope spacing while on a glacier. In Alaska you want to be at least 35 feet apart, as the crevasses are very large there. Make sure you have at least 60 feet of rope on the front and back person. These tails of rope are used to create a mechanical advantage pulley system if your friend falls in a crevasse and can not get out by themself.
Finally, tying butterfly knots in the rope between each person is a very good idea. These knots can wedge in the lip of the crevasse, preventing the victim from falling further, and keeping the victim's bodyweight off the rescuer while they create a snow anchor and transfer the victim's weight onto that snow anchor.