1) Always be experimenting!
Trying to squeeze out more performance out of your program? Don't be
afraid to experiment!
In practice what that means is you setup small, simple throwaway
experiments to establish how things work when you're not absolutely sure
you fully understand something such (e.g., how many times a second a
certain function can be invoked, how the profiler measures blocking IO
or the time it takes a sub-program to complete).