Tips for LP please

Hello...as a freshly minted PGY1 attempting Lumbar punctures...I would love all of your recommendations on how best to minimise failures. While I know the broad overview of technique and have been successful a few times, lately I have NOT been successful with a couple of easy patients and I'm not sure what I'm doing wrong.

I would love to learn from all of your experiences. What you think the most common mistakes are...how to correct them....different scenarios....your tips and tricks. Please do help !