As a knife is used, the edge will tend to "roll over" or turn to the left or right.  This causes the knife to be dull as the steel at the edge of the blade has gotten out of alignment. Quality knives have a degree of elasticity which will allow Whetting (realignment) of the edge to be done fairly easily.  Hold your knife at about a 20-25 degree angle and use a regular cut steel. (if you have Messermeister's knives with the Elite Edge, use a Fine Cut steel, and hold it at a 15-20 degree angle).  For most knives you will want to whet about seven or eight strokes on each side.  The motion is just as if you are trying to slice a sliver from the side of the steel.  Use of a steel does not remove metal, but merely realigns the edge, thereby prolonging the life of your fine cutlery.
 
As time goes by (it will vary from knife to knife) a steel will no longer work its magic. At that time, your knife will have to be reground. You can either send it to a professional or do it yourself.  If you choose to do it yourself, choose your "weapon". You may select either a pull through style (brutal), a Diamond steel, a ceramic sharpener or a bench stone. Any of these sharpeners will regrind the knife's edge to the desired sharpness. ( the diamond "steel" is not a true steel but a steel shaped sharpener that will remove metal with diamond particles).  Merely hold the knife at the appropriate angle (same as above) and grind one side first using about the same technique as with your steel. You are basically trying to slice a very thin sliver from the sharpener. You should see a consistently ground angle all along the  edge with no shiny places. Now turn the knife over and repeat. Your goal now is to create a tiny burr along the entire edge. When that is accomplished, touch up the edge with your steel.  Please do not use any of the "pull through" style sharpeners on your Elite edge Messermeister knives.These sharpeners tend to remove more metal than may be necessary and we do not recommend them.