To start pick a clay pot to transplant into that's an inch or two bigger than your current pot. Next we need to get some more soil. take two parts potting soil and one part sand. Any kind of sand is fine except beach sand and that's because of the sea salt. Also mix in about an ounce of bone meal and an ounce of lime. to prevent the soil from coming out the hole in the center of the pot take a broken piece of clay pot and make sure it's arched up toward you or the top.next fill up the new pot with that soil mix until it's at the level you can place your cactus in the new pot and have it at the same level it was at before.
Now for the hard part taking the cactus out of the old pot. You can use leather gloves but it's amazing how cactus needles go right on thru them. Some needles will even break off in the glove so you will have the pleasure of getting stuck again and again. The best thing you can do is use a newspaper. Take several sheets and fold them at least twice length ways so you can wrap it around the cactus like a towel. You'll find that you can handle a cactus very well and nothing will come thru those layers of paper. tamp the soil around the cactus with a stick and add more soil is need until that pot is almost full. Finally moderately water and place in a warm sunny location.