I like to have plenty of lemons on hand when I clean artichokes. A metallic reaction changes the vegetable's coloring once it is exposed to oxygen; the citric acid from the lemon slows the process by lightly coating the artichoke and preventing discoloration. I use a stainless steel or enamel pot to cook the artichokes, because aluminum causes them to darken. 

Before you begin cleaning the artichokes, bring the poaching liquid to a boil. The water should have ample salt, as well as onion, garlic, herb stems, cracked black pepper and a little white wine if an enhanced flavor profile is desired. 

Using a sharp stainless steel knife, remove the pointy top third of the artichokes, about 1-inch down from the top.  Peel off the dark outer leaves and snap them off at the base until you get to the tender, pale green (or possibly yellow) inner leaves. Rub the trimmed artichoke all over with a cut lemon. 

If the artichoke has a stem, remove the tough end with a paring knife and, with the top pointed down, begin to trim the outer layer and bottom of the artichoke. Rub the cut areas with lemon and repeat with each artichoke.

Once all of the artichokes are clean, cut them in half lengthwise, and add them to the now-simmering poaching liquid. You can use a piece of parchment or other food-friendly baking paper to cover the artichokes and then place a weight, such as a plate, on top to keep them submerged in the cooking liquid. Cooking time will depend on the size of the artichokes: baby artichokes should take about 15 minutes, while mid-sized artichokes will need about 25 minutes. Slip a knife tip through the bottom of the artichoke to test for doneness. If the knife passes through without resistance, the artichoke is done. The artichokes can be slightly under cooked and cooled in the poaching liquid to absorb additional flavor.  If straining them immediately, placed the drained artichokes on a plate and cool in the refrigerator.