In the first place, you must think before promising to take a specific task on yourself. It is a good idea not to operate on automatic pilot when asked to take a project-related responsibility upon yourself, especially if it will involve much time and effort. It's okay to say that you're not sure that you'll get back to the person tomorrow on it. Spend the day thinking of questions which will help you to respond in an honest, thoughtful way. You should only make those promises which you are able and willing to keep. You should only agree to assume responsibilities which you have committed yourself to do.
If your boss insists that you take on a new responsibility, be sure to ask questions to obtain more information. Respond only when you are able to make a reasoned, informed decision, taking into account the time commitment, the specific tasks required, the kind of support available, etc. This kind of interaction with boss and coworkers can actually help everyone involved to think the needs of a project through in a more realistic and complete manner.
Accountability works best when there is regular communication, which includes updates about a project and your individual responsibilities. Whether the communication system is based on meetings or email, feedback is essential to the accountability process.
Accountability also requires negotiating. Don't assume that you must commit yourself to a request as it is presented. Negotiate with your boss and colleagues in print scrub jackets with regard to what you are able to accomplish and what support you will need from them. Remember that negotiation, like...