This is a question that I, of course, have some self-interest in, since I am an outside planning facilitator.
There are two important parts to this question, and they both lead to insights about how to improve your strategic planning.
First, should you use an outside strategic planning professional? Of course, I think the answer is yes, but not always. A professional planner (and by this, I mean someone who does NOT consult on other topics, such as marketing, team-building or manufacturing) can add a lot to your process by stimulating good strategic thinking and giving lots of examples of strategies that have worked at other companies. A planning professional can also take a lot of burden off of your team - by knowing what to do, when to do it, and how much time to spend on it. A highly experienced strategic planning professional will know exactly when to let a conversation run on and when to cut it short, in order to create a strong strategic plan with great support from your strategic planning team. When companies try to do this on their own, they inevitably have difficulties with discipline and buy-in, and worse, the person doing the planning has to divide his or her attention between the planning activity and the strategic content of the plan.
Here are the most common mistakes around the question of whether to use an outside strategic planning facilitator:
1. Not using a strategic planning professional when you need one
2. Using one when you don't need one
3. Using the wrong person
Most poorly written strategic plans that I've been asked to fix over the past twenty years have been the result of either #1 or #3.
Second, who should you use as a strategic planning facilitator? Obviously, an experienced professional who does nothing but strategic planning. Why? Because strategic planning is like surgery - yes, a doctor can do it, but if you need it, you probably want someone who does it over and over again. The difference between getting your strategy right and "pretty close" may only be one or two percent - but that can amount to millions of dollars over time for even a small company.
So what skills should you look for? Here is a list that I have found useful when hiring strategic planning professionals for my firm:
1. Strategic thinking skills
2. Team facilitation skills
3. Solid business understanding
4. The ability to absorb a large amount of information quickly
5. Strong personal integrity
6. Familiarity with a large number of different business models
7. Familiarity with the strategic planning process
Here are some skills which do NOT affect the quality of your plan (although I sometimes look for them when hiring):
1. Experience in your industry
2. Familiarity with the latest buzzwords
3. Sales ability
4. Certifications of any sort
5. Public speaking ability
Hopefully, these comments will help you understand the need for a strategic planning professional, and how to pick a good one.