In reply to 'pistache268's question on knuckle cracking:
Which way do you crack your knuckles? I push my middle ones backwards and my index finger on my left hand forwards.
Interesting, I have a different technique:
I only crack the knuckles closest to my palm. To do this, I use the free hand to pull the tip of the to be cracked finger to the body and push the base of the finger in the opposite direction leveraging a lever mechanism.
Sometimes, I reverse this by pushing the finger tip with the free palm away from the body and pushing the fingers base in the other direction with my remaining index finger.
I used to like cup the finger with two fingers on the other hand and just push back. However some fingers might need a slight adjustment or maybe a pull to get the satisfying crack.