A stone and a sharpening steel are the best, but Ikea makes a decent
knife sharpener that costs about $5. Home Depot also has one that costs
about $7.

They both have preset grooves that you just draw your knife through.
They wear out out after a couple of years, but you you can't find
anything better for the price.

UNDER NO CIRCUMSTANCES should you use an ELECTRIC KNIFE.SHARPENER!
They grind away the edge and can ruin a fine knife after just a few
uses.