A: When you purchase corned beef at the store, it is usually sealed in a vacuum bag with the brine and spices. Take the meat from the package and rinse off the brine.
Put the meat into a pot and cover with water and add the spices. You can also add fresh vegetables if you like such as cabbage, potatoes, carrots, etc. Have enough water so that everything moves freely and is covered.
Most corned beef are 3-4 lbs; cover the pot, bring to boil then simmer at least 3 hours. If your corned beef is usually stringy or tough, it may not be done enough.
The true test is to pierce the meat with a long fork and if it slides off easily, it is done. Remove the corned beef from the pot and let is "rest" until completely cool.
Don't try to slice it while is it hot. It is best to use a slicer, but if cutting by hand, slice as thin as you can.
You will be able to see a "grain" on top of the meat; that is the direction of the 'strings' of meat. You do want to slice it diagonally across the grain; let me explain what that means.
If you slice and it starts to crumble in strings, you are slicing it in the wrong direction. Attached is a photo that shows how the meat should look when it is sliced.