Whetstone sharpening done by hand.
This process may take longer than a belt sander, but I think gives a superior edge whilst loosing the minimal amount of steel off your blade.
*If you have Japanese Knife please DO NOT put it in a grinder or belt sander or any of those pull through sharpeners!
My sharpening progression.
#120
#1000/2000
#5000
Leather Strop
*Depending on the knife, steel type and application.