Let's talk about keeping internal politics out of IT decisions. What practical steps have you taken to make your decision-making process really clear and transparent?

We do try, but admittedly we are not always successful. Often important relationships with other non-IT executives does impact our decisions. Longer term this is needed to foster a positive relationship with our business partners. 
The one thing we do is at least try to capture the impacts of the decision. We have an architectural review board that somewhat independently (I say somewhat as we do have a report to and a desire to stay employed. Blasting your boss's pet project is not a career extending recommendation!) reviews all requests and solutions and identifies the impact of such decisions. We really do not say Yes or No, rather we strive to identify the options and the pros/cons of each. Never have we found a decision that was politically influenced to be wrong. What we mostly see is that it is a solution, just not the best solution.  We thus document the trade offs. 

In addition to ceremonies, setting annual goals and priorities at the start of the year is crucial for alignment. Stakeholder alignment is also essential, achieved through committee meetings or ad hoc discussions. Cross-functional alignment plays a significant role in ensuring transparency and clarity in decision-making, helping to keep politics at bay.

We've established processes similar to those described by Mudit, with ceremonies and quarterly planning. By adhering to predefined processes that incorporate proper checks and balances, we aim to minimize political influence in decision-making. While it doesn't eliminate politics entirely, it significantly reduces it, ensuring decisions are made based on established criteria rather than political maneuvering.