I posted previously about addressing secondary characteristics, but this is a common question for clinicians. So, I thought I'd write a bit more....
Secondary characteristics, or accessory behaviors, include eye blinks, looking away from the listener, tensing muscles in the articulators or elsewhere in the body, moving ones hands, etc. These behaviors can be uncomfortable for speakers, because they can draw more attention to the stuttering itself. Still, they are a common characteristic of stuttering as speakers try to get their words out by whatever means they can.
As a result, it is not uncommon for clinicians, parents, and people who stutter to want to address these in therapy.
One thing to think about when considering secondary characteristics in people who stutter is the reason people look away or tense their muscles or tap their foot or whatever. Typically, these behaviors are viewed as attempts to get out of the moment of stuttering (to get unstuck, as it were). Put simply, the moment of stuttering can be uncomfortable for speakers, and they want to get out of it as quickly as they can. So, they do things to try to force their way out of moments of stuttering, and those things they do are what we tend to call secondary behaviors.
As noted, we generally do want to help speakers diminish these behaviors, because they typically add to the overall appearance of the moment of stuttering. The question is how we go about doing that.
Rather than focusing specifically on the secondary characteristic (like telling a child not to look away or tense their fist or whatever), I'd rather address the underlying reason for their desire to get out of the stutter as quickly as they can -- that is, the discomfort. Here's the problem: if you teach a child not to look away (or tense or whatever) during a moment of stuttering but s/he is still uncomfortable with that moment of stuttering, then it is very likely that that discomfort will manifest itself in some other way. Maybe the child will stop looking away, but he may also then start tapping his foot or tensing his fist or doing something else.
As long as the underlying discomfort is still there, then it will show itself in one way or another. Therefore, the best way to help speakers diminish secondary characteristics is to work on the underlying discomfort itself - to desensitize speakers to the moment of stuttering so they can be in that moment without feeling the need to struggle and tense and fight with it.
Once a speaker sees that he can be in that moment of stuttering without discomfort (or, at least, with less discomfort), then he will no longer have a reason to use the secondary characteristics. The secondaries then diminish as the person learns to stutter in an easier way that is less disruptive to communication.
Focusing on fluency keeps us at the surface level, and that means that the person will continue to struggle because of the underlying fear and discomfort. Focusing on the deeper levels helps to reduce the surface behavior.
As for how we help people become less uncomfortable with stuttering? That’s a topic for another post. Meanwhile, we have a free "Practical Tip" helping speakers become more open about stuttering, available I the “Resources” of the website.