For those who want to build the skills at home to sharpen your knives you'll need some sharpening stones.
While you can remove steel using the curb of the road or grinding paper we prefer whetstones - they will keep the steel cool and allow those that know what they're doing create finely refined edges.
To start sharpening you'll typically use a knife stone with a grit (roughness) of around 250-400. Your second passing will be 1000 and if you want super sharp then finish with a 6000. For those beginning a 240/1000 grit is a great place to start (it has two sides with different grits).