A refresher for checking your lettuce, particularly Romaine lettuce for bugs before Pesach.
We provide three versions of cleaning and checking for bugs in leafy vegetables.
The first is from StarK of Baltimore.  The technique used is called the shmatte bedika (thrip cloth) method and are summarized as follows:

1. Soak the leaves in detergent.
2. Agitate the leaves for about 10 seconds.
3. Remove the leaves.
4. Prepare a 60-micron mesh cloth sandwiched between two colanders.
5. Pour the remaining soapy water through the cloth.
6. Inspect the cloth over a light box.
7. If insects are found, repeat steps 1-6 for up to three times.
8. If insects are still found on the third attempt, do not use the produce.

The second is from CRC (Chicago Rabbinical Council).  Using the chazaka method, the steps are as follows:

1. Add soap or vegetable wash.
2. Soak for 1.5 minutes.
3. Remove the lettuce from the soapy solution.
4. Check the water for insects.
5. If the water is not clear of insects, repeat steps 1-4.
6. If the water is finally clear of insects, take three samples of the lettuce and check each one under good lighting for bugs.
7. If no bugs are found, the rest of the lettuce may be used without further checking.

The third is from the OU.   A brief summary of the steps involved:

1. Soak in soapy solution for 3-5 minutes.
2. Agitate water to shed unwanted materials.
3. Rinse individual leaves under stream of water.
4. Visually check each leaf with bright light source.