Respect the limits of your client abilities
In my experiences, I have noticed you can come up with the most brilliant strategy in the world, it wont help you if your organization can't implement it.
If your football team does not have a strong offensive line, there's no point in running the ball in the middle. Slow down and understand your client, be careful what you promise, engage your client in the process, always pluck the low hanging fruit to start the buy in process.
When gathering data, facts are always friendly, be prepared when conducting interviews guide and listen only. Most important don't re-invent the wheel. Most important keep the information flowing and always adjust to your clients ability to deliver.