This Instructable will show you how to make a suit out of cardboard, but probably not very well, since I only have pictures from after the suit was crafted, but here it is anyway.
Step 1: The Making: Straps Tip
On the straps for the leggings and vambraces, for which I used Duct Tape, make sure to put tape on both sides (double-sided tape as I call it), if you don't then the strap will just stick to your arm or leg.
Step 2: The Making: Torso Support
This will show you how to keep the torso armor from slipping off of you. I advise to measure yourself with the length of cardboard you will use for a strap to know how long it needs to be.
Step 3: Finished Product
The epic finished product. This is what I do when I have a week off of school because of snow days.