Sedum is the workhorse of the garden, picking up the blooming cycle when other plants start slacking off. One of the main problems with sedum is that, because it is so hardy, it will just grow and grow and may become gangly. Overly large showy or tall sedum can be dug up and divided. If your sedum just needs a prune, that's a much easier project.
Wait until early spring to cut back the sedum. Then, choose a cool day and plan to do the trimming around mid-day.
Disinfect your hedging shears by combining one part of household bleach to nine parts of water in a tub or bucket large enough to accommodate the blades of the shears. Allow them to soak for two minutes, then remove them and clean the blades with soap and water.
Cut back the sedum to 3 inches tall with your hedging shears. Start with the outside stems and work your way to the middle.
Pinch off the tip of new stems when they reach 4 inches to keep your sedum looking tidy. This will encourage the plant to grow bushier instead of growing more stems from the crown.