Cut sedum back on a cool morning in mid-July. The plant will be hydrated, and will bounce back sooner after being cut back.
Use a tool with a clean, sharp blade to cut sedum. Household scissors work very well, but you can also use garden clippers. Wipe the blade with rubbing alcohol before you begin to prevent transfer of bacteria.
Prune sedum by cutting all the stems back by half. Remove any stems that look thin or weak.
Keep sedum looking neat by pinching an inch off the tip of the stems after they are about 4 inches tall. Doing this on a regular basis will encourage the plant to develop more stems, giving it a bushy appearance. It will also prevent the need to cut back drastically.