There can be a dozen ways of achieving a goal. In your plan, what you need to do is decide on a set of integrated strategies and follow them. Evaluation, the final step in the planning process, is the most neglected. If you did it's just as important to know why. If you don't know why you succeeded, you can't possibly replicate that success at another time or with another product.
Planning does take some time but the benefits far outweigh the costs.
The process is as important as the outcomes because it is through the planning process that you really get to know and understand your own company. Planning can't always guarantee success but it can minimise the prospect of failure.