Line a large colander with a double layer of cheesecloth, muslin, or another porous white cloth. In a large pot, bring the milk to a rolling boil over medium heat, stirring the milk and scraping the bottom to prevent scalding. Stir in the lemon juice. The milk will curdle and separate (add a little more lemon juice if the milk has not completely curdled). Continue to boil for about 30 seconds, stirring slowly to prevent the large clumps from breaking up. Remove from the heat and pour the whey with the cheese through the lined colander. Hold under cold running water for 15 to 20 seconds to rinse out any traces of the lemon juice. Gather the edges of the cloth, tie them together, and squeeze out as much liquid as you can.
Hang the cloth from the handle of a wooden spoon, and set the spoon over the colander. Allow the water to drain from the cheese for 1 hour at room temperature. To shape the paneer, place the drained cheese, still in the cloth, on a flat plate. Put a heavy weight, such as a Dutch oven, over the cheese. Let sit for 30 to 45 minutes; any excess water will be extruded and the cheese will be firm to the touch. Remove the paneer from the cloth, and cut and use as needed. Store the paneer, wrapped with plastic wrap in an airtight container, for up to 5 days in the refrigerator.