This its the way I tie on crackers. It's fast and easy, and it won't leave a big bulky knot when you are through.
Lay the cracker across the fall as shown
Wrap it around the fall just like you see here. If you want a tighter knot wrap it around two or three times. I personally like to wrap it three times. This will create what is called a "blood Knot" which is very secure.
Now insert the fall through the loop of the cracker and pull the fluffy end tight.