Ask HN: How to passively prepare for a job interview?

Hey there fellow HNers! I am currently at a stage where I am working within a Tech Consulting company for 5-6 years. My plan is to prepare myself well in the next 5-6 months and then possibly start actively interviewing for jobs. How can I do passive job search and interviewing in the meanwhile so that I can setup myself best after few months? I am in a data-science and machine-learning domain.

Thanks!