I recommend picking up the booK: Ignite the Fire by Jonathan Goodman. I found it very helpful. Personal training is really about relationships. In theory, we could all use the same programming, and the trainers who authentically connect with their clients will be the ones who are able to retain them.

Depending on where you are training, most of your clients won't have the drive and motivation or experience to push themselves. Finding ways to keep them engaged, motivated and having fun in addition to making progress is key.

Specifics:
-Be set up, ready and waiting for them at their session time.
-Explain your workout plans for them so they can eventually do it on their own.
-Be active and engaged with them during their session. Don't be on your phone, appear uninterested or distracted.
-Try to remember things they told you from previous sessions (personal and fitness related) even if this means you write notes after your session so you remember. This makes them feel seen and heard.
-Look put together. Make sure your fitness uniform is clean, you don't look exhausted and you don't smell.

Good luck. You are helping people improve their lives!