George Bernard Shaw wrote that, "the single biggest problem in communication is the illusion that it has taken place". Much of strawmanning is unconscious. One person says that it is important to be positive, the other person interprets this as it being important to be positive in *all* circumstances, when they are merely making a general statement.
I would suggest that a technique to avoid accidentally strawmanning someone would be to begin by intentionally strawmanning them and then try to back off to something more moderate from there.
Take for example:
"Just be yourself"
A strawman would be, "Even if you are a serial killer, you should focus on being yourself, than changing how you behave".
Since this is a rather extreme strawman, backing off to something more moderate from here would be too easy. We might very well just back off to another strawman. Instead, we should backoff to a more reasonable strawman first, then backoff to the moderate version of their view.
The more moderate strawman, "You should never change how you act in order to better fit in"
When we back off to something more moderate, we then get, "Changing how you act in order to better fit in is generally not worth it"
You can then respond to the more moderate view. If you had responded to the original, you might have pointed out a single case when the principle didn't hold, such as making a change that didn't affect one's individuality (i.e showering regularly) and used it to attack the more general principle. When you have the more moderate principle, you can see that such a single example only negates the strict reading, not the more moderate reading. You can then either accept the moderate reading or add arguments about why you also disagree with it. If you had skipped this process, you might have made a specific critique and not realised that it didn't completely negate the other person's argument.