Here are some tips for establishing rapport when using Rapport-Based Communication. This understanding comes from my experience of mentoring practitioners working in a variety of learning disability and dementia care settings. Quite often the practitioners is doing nearly everything right but just misses one of these things which results in a lack of rapport.

Eye level - at the same level or lower than the person you are supporting
Proximity - sometimes practitioners are too far away or too close to the person
Be available - make sure that you are positioned so that interaction is easy
Everything you do should be a response - use the 3C’s to respond to the person
Reflect on what you are doing - you should learn something from each encounter
Same pace - adjust your pace to the person
Leave space - for the person to respond and try initiating
No demands - find a way to share the space with the person without expectation