When a coach starts a new job, the most common approach is an enthusiastic zeal to fix everything that is wrong and to install all the right things. This zeal dictates that everything should be done sooner rather than later, and preferably in the first week.
The first consequence is that players are overloaded with new information. If the players are not beginners, then a lot of that new information will conflict with the information that is already in place.
The second consequence is that the coach will very quickly be frustrated by the pace at which changes are being made, or plans are being implemented. New information needs time to be processed. Conflicting information requires a different approach and takes even more time.
By all means, a new coach must have a plan. But be careful about the time frames you allow to implement it. Everything good takes time, and for a new coach in a new situation, often the best approach is to take baby steps.
A collection of 50 Coaching Tips can be found here.
For more great coaching tips, check out the Vyacheslav Platonov coaching book here.