Action
Avoid isolation (the 'lone ranger' syndrome) which is a real transition killer. Find trustworthy people you can meet with who understand leadership and the organisation.
Risks/Opportunities/Surprises
Avoid a 'folie a deux', that is, a relationship where you reinforce each other's delusions. Find people who can safely challenge you.
It is important that your key relationships help you focus on your situation, as it really is. While emotional support is important, collusion that lets you avoid issues will undermine your viability as a leader. As such, not only must you have people who can be realistic, informed and honest, you must ensure you can manage yourself, willing to put aside your own assumptions if they don't match the facts.