Unlike randomly cracking the neck, which may take your spine out of alignment, back cracking can mobilize the spine (a good thing). There are a quite a few ways to crack one’s own back.

On a chair
It’s been known for the lower back to take the worst usually, so here is a very good and effective way to relive tension. Ensure that the chair is hard without a cushion, or a fluffy seat etc.

Sit on a chair and place both hands on either side of chair, gently gripping the end.
Slowly slide down the chair so that your bottom is slightly off.
Relax your self. All your weight will suddenly shift to your lower back thus cracking it. Sometimes it’ll be a sudden jolt, or be little. It may crack it all in one or in sections.
(Alternatively, you can stand up, press the palms of your hands on your lower back and bend backwards to crack it. Not as effective and causes discomfort during and after.)

Stretch and Pop
Works like a charm in the mornings when your back is completely relaxed after just waking.

Place both hands to the back of your head (like how police arrest people)
Calmly push your head backwards into your hands and arc your spine so that your stomach sticks out and your back should crack, remember to stretch afterwards

Bear Hug
This is good to correctly crack another person’s back and not your own.

Stand face to face with a person of equal or smaller size to, have them take ten deep breaths and relax,then proceed to lift the person in a bear hug with your hands clinched into one large fist and align your clinched hands with the lower centre of their spine.
As you lift them squeeze the person gently (like a bear hug) and let them gradually fall back down meanwhile alternating pressure as they drop cracking each vertebrae along the way. This is an extremely effective and safe way to crack a person’s back other than your own, and it lets their back align naturally instead of twisting.
The key is that the person has to be relaxed, if they hold in their breath as you squeeze it will cause more harm than good.

Sit on the Floor
Sit on the floor with one leg bent and the other leg out (doesn’t matter which, you will switch and do both sides).
Make sure your bent leg’s knee is up (with the sole of your bent leg on the floor).
Place the opposite elbow of the bent leg on the outside of the bent leg’s thigh or knee.
Look as far as you can behind you (starting toward the bent knee side).

Lie on Your Back
Lie on your back on the floor with your left leg straight and your right leg bent.
Keep your right shoulder on the floor and move your bent right knee as far left as you can and slowly stretch.
Repeat both exercises on the other side (opposite leg).

Lie Face Down
Lie face down.
Turn only your torso so your right shoulder supports your weight.
Extend your left arm and stretch in the opposite direction that you’re facing.

Lie Down
Lie down to get comfortable.
Fold your arms like you’re flexing.
Put arms on chair, bed, or on ground.
Push back forward until it cracks.

Sit on a Chair
Get a chair.
Sit facing forward.
Hold the left post of the chair with your right arm.
Turn your body to the left.
Repeat using the right post.

Lie Face Down on the Floor
Ask a friend to help.
Lie face down on the floor.
Have your friend sit on top of you and place hands on both sides 2 inches from the spine.
Apply pressure starting from the bottom of the spine until you feel popping.
Keeping moving up the spine till it’s all cracked out.
Do not apply pressure near ribcage/lung area.

Cross Your Arms
Cross your arms across the front of your body and touch the opposite shoulder so your elbows are crossed.
Have a friend behind you reach around and grab your elbows
Have your friend pull your 2 elbows towards the opposite shoulder of the arm while picking you up
Your friend should then push your back with his or hers chest.

Stretch Both Arms
Lie on your back and stretch both arms out horizontally. Having something to grip, such as a table or chair leg, helps.
Bend your right knee until your thigh rests against your torso.
Keeping your arms out, twist your body to the left, as though you were trying to touch your right knee to the floor to your left. Back should pop.
Repeat with left side.
Lie on the floor. Put your hands back as far as they will go. Slowly do the “bridge”, where you lift up your body with your hands and feet your back should crack.

On the Floor
Kneel on the floor on both knees, about shoulder width apart. Be careful if you have bad knees.
Hold your arms straight out to your sides like a T.
Arch your back slightly and twist, as if attempting to touch your right hand to your left foot and vice versa. If you can touch your feet, great! If not, don’t push it! It should work regardless of how flexible/inflexible you are.

Against a wall
Stand facing a wall
Take a deep breath in
Ask a friend to push your upper back against the wall as you breath out. Do not allow your helper to injure you, take the step by step and talk it through while doing this.
Lean back on a chair
In order to crack my back get a chair, just a regular chair from the kitchen and sit with my back straight on it. Then lean back and the wood at the top of the chair should be about shoulder level.
Lean back quickly and you should get a satisfying crack.

Standing Twist
Stand straight.
Put your arms in front of you, in a bent position, with closed hands. It should look like you’re going to give someone a hug, but instead with open hands, with fists.
Swing your arms to the left, using momentum to twist your back. As you’re turning, arch your back to where the stomach is sticking out.
Repeat, except to the right.

Lying Down Twist
Lie down flat on your belly, feet together.
Rotate your legs ONLY to the left or right, without moving your upper body. A little is OK.
Repeat. Except rotate your legs in the opposite direction as you did before.
Return to the original position.
Rotate your upper body and not your legs to the left or right.
Repeat. Except rotate your upper body in the opposite direction as you did before.
Return to the original position.
Flip over so that you’re lying on your back.
Repeat steps 1-7 lying on your back.

Consult a chiropractor for additional stretches and/or manipulation techniques. You should never attempt to adjust your own spine. Use caution exercising any of these techniques.
Overly mobile vertebrae can be very dangerous and painful.
Be aware of the pressure you are applying when trying to crack your or anyone Else’s back. If you or your partner start to feel an ache or pain stop immediately. Pain tolerance is different for everyone and if you are trying to crack someone’s back and you feel you are applying too much pressure without the person complaining you should consider another technique.