A meat tenderizer can be one of two things. A meat tenderizer can refer to a specific mallet that is used to pound the meat until it is tender. This is also called a meat mallet. Meat tenderizer can also refer to powder often found in spice racks. Powdered meat tenderizer has enzymes that help to break down the fibres in meat. There are ways, though, to tenderise your meat without the use of a mallet or powder.
Place meat in between two sheets of cling film. Using a rolling pin or heavy iron pan, pound the meat. This will help to break up the fibres in the meat just as a meat tenderizer would.
Cut shallow strips -- a fraction of the meat's thickness -- into the meat. Place the meat in a shallow dish and pour marinade over it. The marinade chould have an acidic component, such as citrus or vinegar, which enhances the tenderising effect.
Cover the dish and allow to marinate. If using acidic or especially salty components, limit the marinde time to a couple of hours, as the acid would eventually break down the meat too much. The longer it sits in herb-based marinades with, say, olive oil, the more tender the meat will be.
Stew or cook your meat for a long time at lower temperatures. The longer the meat is cooked -- using the "low and slow" method, referring to temperature and time, respectively -- the better chance your results will be tender and juicy.
When plating your meat, cut across the grain of the meat. This cuts across the fibres in the meat that can sometimes make it chewy.