How can I repot my cactus?

Get some thick leather gloves to avoid the cactus spines. Choose a larger container (one size up) for the cactus and add fresh cacti soil to the new container. Run a knife around the existing container to loosen the soil, then lift out the cactus, holding either with newspaper or barbecue tongs. Clean and inspect the roots, pruning if necessary, then allow to dry for a few days. Then pot the plant (holding with newspaper or tongs again) in the new soil and pot. Wait a few weeks before watering, to give the transplanted cactus a chance to settle in. More detailed instructions can be found here: How to Report a Cactus.