Each person intuitively figures out what methods work for them. Our job is to watch carefully and take note. A person might make different gestures for different things. A person might make a certain sound to convey a particular message. A person may already be using signs or gestures. They might use other forms of simple messaging. We never want to take away, or disregard, what works for them. The best way a person communicates is usually a combination. Several modes and symbol systems at the same time. This is different for each person. Each person uses what works best for them.
The best way a person communicates might be through frustration. Some people who don’t talk get frustrated. They might have had years of not being able to get their point across. They might have figured out that heightened emotion gets noticed. We want negative behavior to stop. We don’t want communication to stop. What does the frustrating behavior communicate?
The best way a person communicates might be subtle. Some people who don’t talk, shut down and become passive. They have experienced roadblocks and failures when they try to communicate. The accumulation of these tiny failures build until the person gives up. They might seem like they don’t want to communicate. Their lack of engagement makes their communication more subtle. We might have to really get to know them.
There’s not just one “best” way to communicate for each person. Each person creates his or her own “best” way by combining whatever works. Most people use a lot of different tools to create their own system.