Final answer:
Common processes to close to improve system performance include resource-heavy applications like web browsers, video editing software, and background updates or scans. Use Task Manager or Activity Monitor to identify and close these processes.
Step-by-step explanation:
When a system is running slow or not responding, the most common processes to close are those that are using a high amount of CPU or memory resources. To identify these processes, you can open the Task Manager on Windows or the Activity Monitor on Mac. Look for processes that have high percentages next to CPU or Memory.
Often these include web browsers with many tabs open, video editing software, games, or any software that is not optimized for your system. It's also important to check for background processes related to software updates or system scans which can slow down your system. Be cautious when closing system processes, as this can cause stability issues.