hiring timing really depends on location and on role.
For example, I know that in the McKinsey Milan Office there are four main intake: January, March, September and October, both from Business Analyst and for Inter. For each intake, the recruiting period is about 3 months before, hence the interview preparation should start at least 6 month ahead (my case: I start my prep in Feb, I start the recruiting process in April, I did my interviews in July and I started as Business Analyst in October).
In terms of networking, check out for specific event on the webiste. I attended the women lunch in January and that was my first contact with McKinsey and it helped me a lot in terms of networking and preparation planning.
Hope it helps! :)