What are the advantages to planning?

Question

What are the advantages to planning?

Answer 1

Planning is 90% of each job as I like to say.

First there is no confusion.

There is no waste of material or time.

There are measurable accurate results.

There is less room for error.  

Answer 2

to add to others.  Planning finds the critical path, ie you get done in the quickest time with the least amount of resources.