Do not act based on Assumptions. Ask a lot and do the research before taking action.
Verbal communication does not count, document anything via documents or e-mails to save them formally.
Always set the right expectations when dealing with a colleague, a manager or a customer, especially when you are expecting delays, new changes, or when saying no to an offer or a task.
Make sure that your effort is showing up to your managers. Working too hard in shadows will not help.
Work effectively. Do the right thing with the adequate effort, instead of paying too much effort but in vain without getting any needed results. Imagine two football teams, one plays too hard and run a lot, and the other scores. The latter knew how to benefit from chances they had, also how to utilize their efforts right.
Delay when Angry. Never respond to an e-mail, or verbally, while you are angry. I remember a motto that says the best cure of anger is delay. Delay your response back for a day and believe me you will be surprised that you have responded in a completely different way than replying instantly while you were agitated.
Your career development is totally your responsibility. Despite the company and your manager may offer support in that regards, still you need to take the lead and ask for all development opportunities you need to take.
You cannot please everyone in the workplace. Seeking the satisfaction of your CEO, all managers and all colleagues/employees is a myth. Always program yourself to do the right thing, following the company management decisions, rules and regulations.
Unlike your group of friends in school or college, do not expect work colleagues to cover you up, or act for your favor. In corporate world everyone will secure himself/herself, saving their jobs and paychecks. Be prepared for that.
Do not participate in grapevine or office gossip. Talking about only one employee can show to others that you can also gossip about them.