You cannot be "successful" unless you know what you are striving to achieve.
How do I know if the coaching has worked? (Assessing Outcomes)
In order for coaching to work, you need to start out with goals of some kind -- and we will work on establishing those goals together.
You will need to set daily intentions and have accountability structures built into your week.
If you are a corporate client (or a client whose parents have hired the coach), you will need to create status updates for key stakeholders (or parents), so that they can see the progress you are making along the way.
You must also give the coaching time to take root. Behavioral change doesn't happen overnight. Corporate coaching usually is set up to last six months or a year, depending on the circumstances.
Coaching of individuals (where there would not be 360 assessments, nor stakeholder meetings, etc.) generally requires at least three months, with six recommended.
Team coaching should not be undertaken (or assessed prior to) for less than a six month period of coaching -- there are too many dynamics at play to build sustainable change in less time. However, if team coaching is desired for a year's time, a "mid-way read" would be done at six months and then again at the end of the year.
That said, there is no way to "guarantee" success or do an "ROI" analysis. Coaching is so highly dependent upon the attitude and effort of the client, and there is no easy way to quantify the "value" other than to decide if you accomplished what you set out to achieve or not.
If at any time you become unhappy with the coaching, you should bring your concerns to the immediate attention of the coach so that these concerns may be addressed. The coach will not be angry or hurt by your feedback, and a good coach will welcome continued check-ins and adjustments to the coaching process.