Obtain your lumbar puncture needle. Check that the stylet slides easily out of the needle prior to use. If using a beveled needle, ensure it is oriented correctly (the notch on your stylet should point towards the ceiling). Now recheck your lumbar puncture site by palpating the posterior superior iliac crest and ensuring you are in a correct spinal interspace. Position the needle in the same way you did for the anesthesia. It should be placed two thirds of the way towards the distal spinous process. Ensure the needle is parallel to the bed and aimed at the umbilicus. Advance the needle. A 'pop' will often signal the puncture of the ligamentum flavum and dura. When this occurs, replace the stylet and advance the needle slowly while repeatedly removing the stylet and checking for CSF flow.