Hints on choosing a setting
1. Different applications behave differently when a system resource such as QuickTime fails to load. Some will warn the user, some will just not perform a particular function and some will crash.
2. Just because an application starts up normally, it doesn't mean that the free memory allocation is correct. You need to exercise the application to know for certain. For instance, some games play quite normally, but will not play the cut-scene movies.
3. The crash may not happen until you quit the application. This is still a symptom of having too little free memory.
4. If you are running a server application that launches other applications (CGIs for instance) you may need to leave quite large amounts of free memory.
5. An application that uses QuickTime, especially for playing movies, may need more than 1.5MB free memory.