Step one: remove the cone
Remove the quick release from the axle. Our demonstration is with a rear wheel, and so the cassette must be removed too (insert a cassette removal tool, hold the cassette in place with a chain whip, unscrew the cassette by applying an adjustable spanner to the removal tool and turning anti-clockwise).
Apply the cone spanner to the non-driveside cone (15mm in this demonstration, but 13mm and 17mm are popular sizes too) and a second spanner to the lock ring (typically 17mm) and unscrew the lock ring by turning the spanner in an anti-clockwise direction. Remove the lock ring and spacer, carefully placing them to one side in the order in which they were removed.
Unscrew the cone, place it with the spacer and lock ring, and carefully remove the axle from the hub. The bearings will now be held in place only if any grease remains on the cup, so carefully place the wheel to one side, either standing it on its rim, or laying it on its side over a box or tray.
Clean both cones with a rag and degreaser, and inspect for wear. A worn cone can have a pitted surface. When the bearings are tightened against it, the wear can be felt, making the wheel rotate roughly, with an almost ‘indexed’ feel.