A smart question will have important characteristics that make the question clear, informative, and to-the-point for the right community. Details like the specific versions of their environments, and symptoms of the problem are important for the specific community that you are asking. Another characteristic of a smart question is to describe steps and research that you have done to understand the problem, so that the community has some context of the solution you are looking for. One of the strongest things that can be included in your question is to have a way to reproduce the problem to have a clearer view of any chronological events that can lead to the problem.
Here is an example of a smart question. First, he provided the environment of his problem, and included the specific versions of his programming languages and any backends. Then, he proceeded to describe his problem and included research of other solutions that were similar to try and solve the problem. Then he included some code that might have caused the error and described what it does. He also has shown that he changed the code several times and got the same error. He also included the exact error message that was returned.
https://stackoverflow.com/questions/63841807/i-dont-know-why-is-arraylist-size-showing-error
This is an example of a bad question because they do not show any details. They did not give any information of their environment, or the error that they have received. They did not know which part of the code could have had the potential problem, so they might have not done enough research. They only have shown the code, and have mentioned that it does not work. They did not show the exact error message that was returned, or anything that was helpful.