It is best to think of planning as a cycle, not a straight-through process.
Once you have devised a plan you should evaluate whether it is likely to succeed. This evaluation may be cost or number based, or may use other analytical tools. This analysis may show that your plan may cause unwanted consequences, may cost too much, or may simply not work.
In this case you should cycle back to an earlier stage. Alternatively you may have to abandon the plan altogether – the outcome of the planning process may be that it is best to do nothing!
Finally, you should feed back what you have learned with one plan into the next.
