Before setting out, be aware that this is a highly demanding route. Start on the Iztaccíhuatl - La Joya a las Rodillas (From La Joya to The Knees)
route. That run is especially grueling from the 100 Shelter (4700m or 15400ft) to the Knees (5033m or 16500ft).
After you pass the Knees, you are in pretty good shape to summit the mountain, and you'll know what kind of terrain awaits. After another steep section of trail, the run will flatten out. Use this plateau to rest, as the final push to the summit is steep! Just before the highest part, you have to go across a small glacier which demands the use of crampons if the weather is harsh. If conditions are right and if you are careful, you can continue on your way without them.
I strongly recommend to start the route very early in the morning (1AM) to reach the glacier by 8AM and enjoy an amazing view of the sunrise.