Making a Heavy Bag
Start with an army-style duffel bag. You can find one at an Army-Navy store, order one online or even luck out and get one cheaply at a yard sale. Be sure to look for one that is heavy-duty and made of weather-resistant material. This will be the main component of your heavy bag and needs to be able to withstand weathering and major daily punishment.
Take all your old and worn-out clothes and cut them into small rags, or just use rags. When you have a considerable pile, start stuffing the bottom of the duffel bag. Sprinkle a few handfuls of sand over the first bunch of rags and continue stuffing. Keep pouring sand over the rags as you stuff the bag to the top, but don't overdo it. Ideally, the bag should be about 75 pounds once it is completely stuffed.
Get out the chains. Attach the carabiners to the bag at three points around the top band. Make sure to penetrate two or three layers of fabric with each carabiner to be safe. You will have three mounting points for the chains. Connect three of the chain links to the carabiners and connect the other ends of those chains to each other with another carabiner. Some bags have metal holes around the top band for a drawstring. Carabiners come in smaller sizes, but don't go so small that they won't last after a few uses of the bag. Try to find a bag with larger metal loops at the top that will allow larger carabiners to be attached directly through those reinforced holes.
Find a place to hang the heavy bag. A tree branch is ideal for outdoor hanging. Use heavy-duty nylon climbing rope that will pass through the links of the chain. Attach the fourth length of chain to the end of the rope and make the initial knot adjustable for moving the bag up or down once it is mounted.
You could also buy a swivel bracket at any sporting goods store or hardware store for mounting your bag on the ceiling. Use the fourth length of chain and connect it to the swivel bracket first. Install the bracket in a ceiling beam that will be able to handle the weight and the major pounding. You will also want to choose an area where you can also move 360 degrees around the bag without obstacles.
Hoist the bag up and get someone else with a stepladder or stool to connect the fourth chain to the carabiner connecting the three chains together. Secure the rope knot for outdoor mounting once the bag is set in position. Now it's time to go wild with the duct tape. Seal up every place water might get in if the bag is outdoors. If your bag is mounted indoors, simply wrap the striking areas in duct tape.
Homemade Medicine Ball
Find an old bowling ball at a yard sale or flea market. Try to look for a 10-pin type, but not too big or too heavy. You will want to use this to throw and be thrown at you for strength and conditioning, so keep that in mind.
Wrap the ball from multiple angles with the bubble wrap. Try to apply a thick, even layering around the ball.
Enclose the whole bundle with duct tape, being careful to apply as much tension as possible as you wrap for a tight seal and a lasting outer skin. You may use two or three rolls of duct tape for a larger medicine ball. You can use this to exercise your abs and upper body.