As already stated, for a truely sharp knife, a good whetstone is unbeatable. The one you'd look for is about 3 inches wide and 10 inches long. It's about an inch and a half thick with two different sides. One is more coarse and is used for re-shaping the blade, while the other is finer and used for final finishing. The stone should be placed on a firm surface with a non-skid mat uned it. The blade can them be held at the proper angle (about 20 degrees) while moveing the blade only in a cutting motion (that is, against the blade) applying pressure with the fingertips along the length of the blade. The stone should be bathed in water often during the sharpening process to keep the stone clean. In fact, scrubbing it with a stiff brush every so often is good for the longevity of the stone. Some people use oil, which is OK, but it leaves a dark stain on any surface it comes into contact with.
I've a stone that has to be over 100 years old given to me by a Grandfather who was a blacksmith and made many of his own knives...
Good luck!