Slice off the stem of the artichoke, leaving about 1/2-inch, and remove the lower leaves.
Cut off about 1/2-inch from the top of the artichoke. Rinse the artichoke under cold running water, gently opening the leaves if you are able. Turn the artichoke upside down and let it drain over the sink before returning to the cutting board.
Rub lemon juice on the cut surface to prevent browning. Personally, I don't always do this step because I usually roast or steam my artichokes, which causes them to lose their color anyway.
Use kitchen scissors to snip the tips of the outer leaves, to yield flat edges. Your artichoke is now ready for boiling or steaming. Whole artichokes can also be roasted, but I prefer to cut them in half before roasting and remove the fuzzy choke from the center with a spoon.
Cut artichokes react with air and will turn brown, so it's best to clean and trim them just before cooking.
When selecting artichokes at the store, squeeze them to see if they squeak, which is a sign of freshness. The leaves should not be cracked or overly dry, but some browning on the outer leaves is normal.