Pick Your Battles

There is a reason why things are the way they are. There is a reason why the people here do things the way they do here. Don't be too Gungho, charging on with full steam hoping to make revolutionary changes. Else, you'll end up stepping on people's tails and making enemies faster than you can blink your eyes.

Focus your energy on major quick wins to raise your profile 1st, then when your position is stable and until your stakeholders worship what you say.. then you start the thorough 'spring cleaning'.

Survival Lesson #3:
You gotta pick your battles. Choose those that you have higher chance of winning. Don't waste your efforts on those minor ones.