While optimizing your module can be a tedious task, what so ever do not over optimize it, you could be putting that time to adding more functions to your module to make it more useful. Unless it is a core function that the module calls constantly.
But here is a list of some things you can do, others can chime in as well.
- Don’t use deprecated functions
- Refactor your code, (Is this readable and efficient)?
- Get others feedback.