Prepare a plan that is success oriented, achievable, defendable, and cost-effective but which can absord the changes that will come. Have a contigency plan for each identified risk. Develop a plan that reflects organizational commitment to systems engineering. Perform each task according to the plan. Change the plan as soon as experience shows a better way to do a task.
Planning is everything.
It is a process which transforms an operational need into a description of system parameters and integrates those parameters to optimize the overall system effectiveness. IBM Federal Systems Company definition used as the basis for divisions, internal SE practices and education. Summary definition in the introduction of the manual. The transforming of an operational need into a description of system performance parameters and a system configuration. More extensive defintion found in the glossary.