Determining the appropriate work_mem value depends on several factors, including your system's available memory, the size of your database, and the complexity of your queries. A good starting point is to monitor your current performance and gradually adjust the work_mem parameter. Tools like pg_stat_statements can help you analyze your query performance and identify bottlenecks. Generally, setting work_mem too low can slow down your queries, while setting it too high can lead to memory exhaustion and system instability.