Lean inwards. Leaning towards someone indicates your desire to engage with them.
HELPFUL HINT:
Don't lean in too far - as it can intimidate the speaker.
DID YOU KNOW?
Listening is a gift, so give generously. As you become a better listener, you will most likely find your job more enriching and you will become more successful. Why? Because you will be interacting more; you will be more involved and engaged. You will have more information and be better able to spot opportunities and solutions.