Prepare your potting soil in a separate bucket. Pour some soil into a large bucket and add water to it until it is damp. Mix the soil with your hand or a trowel until it is evenly damp. Do not allow the soil to become soggy, or the seeds will rot. You will need a well-draining soil. Lemon trees love water, but they hate to sit in it.
Try to get a pasteurized soil mix. Pasteurization gets rid of any bacteria that can kill seeds.

Choose a small pot with drainage holes. The pot should be about 3 to 4 inches (7.62 to 10.16 centimeters) wide, and 5 to 6 inches (12.7 to 15.24 centimeters) deep.

This pot will be enough for one seed. Some people like to plant several seeds in one pot at a time. If you want to do this too, choose a larger pot.
Your pot must have drainage holes. If your pot does not have any, you will need to drill some.  Fill the pot with soil. Stop when the top of the soil is about 1 inch (2.54 centimeters) from the rim.  Make a ½ inch (1.27 centimeter) deep hole in the soil. You can do this using your finger or a pencil.  Choose a plump-looking seed from a lemon. It may be necessary to use an organic lemon because seeds from a non-organic lemon may not sprout. Also, avoid taking any seeds that look too tiny (like a grain of rice) or that look shriveled (like a raisin). These seeds either won't sprout or won't grow into healthy seedlings.
Consider planting 5 to 10 lemon seeds at one time, in case some of the seeds don't sprout or don't make it past seedling-hood.
Keep in mind that trees that come from seeds are not identical to the parent tree that they came from. Sometimes, the fruit that the new saplings produce is of a lesser quality. Other times, they do not produce edible fruit at all. This does not prevent the young tree from being visually pleasing. Keep this in mind when growing your tree.

Wash the seed to get rid of the slimy coating. You can do this by washing the lemon seed or by sucking on it until the coating is gone. This is important. The gel-like coating contains sugars, which can cause the seed to rot.

Drop the seed into the hole and cover it up. Make sure that the pointy tip is pointing downward into the soil, and the rounded part is pointing upward towards you. The roots will come out of the pointy part.

Cover the pot with a piece of breathable plastic to trap warmth and moisture. Begin by placing a sheet of clear plastic cling wrap over the pot. Wrap a rubber band around the plastic wrap to secure it to the pot. Poke a few holes into the plastic wrap. You can use a pencil, a toothpick, or even a fork. These holes will allow the plant to breathe.

Place the pot in a warm location. You can place the pot in a sunny location too, but sunlight is not vital at this point. In fact, too much sunlight can "cook" the young, delicate seedlings. You should see a sprout emerge in about two weeks.  Water the soil when you see it become dry. The plastic wrap should trap the moisture, and the condensation should rain down onto the soil, making it damp again. In very dry environments, this may not happen. If you see the soil start to become dry, remove the plastic wrap and water the plant. Be sure to re-cover the pot with the plastic wrap when you are done watering.