Step 1: The Ingredients
Maseca is a dehydrated cooked corn meal product. You can treat your own dried corn with lime, cook it, dehydrate, and mill it yourself, but this is much much easier. It's widely available in Latin markets, or the international aisle of any decent supermarket.
Step 2: Hydration
Combine 2 cups of corn meal with about 1 1/4 cups of water and try and form it into a ball. If it looks like the picture here, then add water a tablespoon at a time until it comes together.
Step 3: Let it Be
Once you're able to form the whole mass into a ball, cover it in plastic wrap or a moist tea towel, and allow the dough to finish up its hydration by resting for 10 minutes at room temperature.
Step 4: Line the Press
Slit open the sides of a gallon-sized zipper-lock bag and place the seam at the hinge end of your tortilla press. This will keep the dough from sticking to the press. Place a 2 tablespoon-sized ball of dough on the bottom plate, towards the hinge side of the press (to compensate for the fact that the dough gets pressed away from the hinge).
Step 5: Press On
Close the press and press down as hard as you can on the clamp. If the dough squeezes out the sides of the press, you've used too much. Use a little less next time.
Step 6: Peel Off the Plastic
Now open the clamp. Don't peel the tortilla off the plastic—it's fragile, and will probably break. Instead, pick up the entire piece of plastic with the tortilla attached and flip the tortilla onto your hand, then carefully peel the plastic away. Stack the uncooked tortillas draped over the edge of your cutting board so that you can pick them up more easily as you cook them.
Step 6b: The Pan Method
If you don't have a tortilla press, you can flatten the balls by placing them in a split plastic bag and pressing down firmly (as in, as hard as you can—put your full weight on 'em) with the bottom of a heavy skillet.
Step 6c: Pan vs. Press
The pan-made tortilla on the left will never be as thin as the press-made tortilla on the right and takes significantly longer to make. I highly recommend you invest in one if you plan on making tortillas more than once or twice a year.
Step 7: Cooking
Preheat a non-stick or cast iron griddle over medium high heat for a few minutes then place the raw tortillas directly on it (no oil). Cook them until the first side is starting to blister into tiny bubbles, but has not taken any color, about 1 minute. Flip the tortillas, press down on them with a spatula to ensure good contact with the pan, and cook for a minute longer.
Step 8: Stack 'em
Place the cooked tortillas on a plate lined with a clean dish towel. Fold the corners of the towel over the tortillas to keep them warm while you cook the rest. The tortillas should steam and soften inside the dish towel, making them moist and pliable.
Step 9: What if They Get Cold?
If you can't serve the tortillas immediately and they get cold, the best way to reheat them is to first dip them into a bowl of water, then...
Step 9b: Back on the Griddle
Place them back on a hot griddle. Cook until the water evaporates and they can be removed easily without sticking, about 30 seconds per side. Re-stack them and keep them wrapped in a clean dish towel.