Good quality modern knives are made from high carbon stainless steel. This combines the softness of carbon steel for ease of sharpening with the strength of stainless steel. High-carbon steel blades tarnish easily but they sharpen to a better edge. The blade is also more flexible. Careful maintenance is required the blade must be wiped dry after use and needs to be washed after cutting acidic produce such as onions.
Look for sturdy construction with the tang (handle end of the blade) running inside the handle and attached solidly with rivets.
The heel at the wide end of the blade reinforces the blade and protects the fingers.
Choose the right knife for the job. Flexible or Rigid, long or short bladed.
Handle
How id the handle made is it plain hardwood or an alegant rosewood? Is pit a synthetic handle, with easier care and more grip and won't crack. Take the size of your hand into account: is it to large or small for the size of your hand?
Construction
Stamped blades are less expensive than forged blades because they are stamped out of sheet steel with shaped dies. Forged knives are now largely mechanically made put the process is similar to the old hand forging.
Tang
The tang is the end of the blade to which the handle is attached sometimes with rivets sometimes molded into synthetic material. If the tang doesn't pass through the entire handle it could cause the khandle to snap or the blade to beacome loose with prolonged use. The full tang is where you get the weight, balance, and stability of a high-quality knife. The best knives have full tangs.
Bolster
This is the thick piece of metal between the handle and the heel of the blade, it is a shield between the fingers and the cutting edge and it helps to the balance of the knife.
Blade
The size and shape of the blade are important to the use of the knife. Select the right blade for the task at hand.
Ceramic
Ceramic blades are light and extremely sharp when made though they cannot be sharpened at home once they lose their edge. The edge will slide across some surfaces such as onion skin rather than slicing through it.