As with every service, choosing the person(s) to deliver it is crucial to the success of the endeavour. Coaching as we know it today is a fairly new field, which additionally confuses clients in their attempt to choose a professional that is best able to address their needs.
In choosing a coach, the most important thing to remember is What Executive Coaching is Not. Understanding each of the different development approaches and their goals will help you decide which skills set to look for in your search.
Therefore, clients should forget about skill sets they are looking for in their corporate trainers for example, consultants or mentors. Instead they should ask themselves whether the coach they are interviewing is helping them look at things from a different perspective or constantly supporting theirs; whether she/he is challenging them or going along with what they hold as true; whether she/he is making them stretch and feel uncomfortable at times, or feels more as an agreeable friend, etc.
And if still uncertain, invite a trained Human Resources professional to assist you with screening. Somebody who is familiar with the coaching field will know what to look for in a coach.