One of my favourite scriptures on knowing God is found in John 10: 1 – 6 (http://bit.ly/2ra4M1E).
It’s all about hearing / recognising His voice.
BUT how do I know it’s His voice?

When your parents call for you in a crowd (or shopping centre), you know it’s them calling for you. How or why? You have learnt to recognise their voice! This comes from spending time with your parents – growing up in their household.

Likewise, the more we spend time with God (quiet times) or sit with the Bible (God’s CV), we will learn to recognise His voice.

Just sit still with Him
Just sit still
Sit still