The key to being a good crew chief is surrounding yourself with good help. It doesn't matter how sharp you are if the people helping do not buy into what you are trying to do and add their own "tuning" aids or are not doing their job the same each time. That is the reason a crew chief will change teams and go from being "unskilled" to "brilliant" in a heartbeat, or vice-versa.
A good crew chief is a problem solver and very analytical and can quickly adapt to what ever his focus is on at the moment. Today they also need to be a "people person" and manage a group. That is the main reason for a co-crew chief or car chief, they are usually the people managers and allow the crew chief to concentrate on what he does best.
You will see that when some crew chiefs change jobs they take several people with them. That will give them a better chance of instant "success" on the new venture. Examples are Paul Smith and AJ, they have their own people where ever they go to tune a car.
Another example, I helped a new team earlier this year at a national event. When I tried to organize the crew and put responsibility onto each crew member, I was told "they are only volunteers" and shouldn't be expected to do what I was asking. I let them do it their way knowing that the owner was going to spend much more money than if he had a paid crew and that success was not going to happen. And I turned down the offer to help them at the next event.
Back to the question, a good tuner can tune anything if he wants.
suspension? 
