Debug your app
Titanium has a debugger! Some of you will not be excited by that, but to those people who coded in Titanium before the debugger existed, it is a blessing. If your code is well structured and modularized and with small functions, you probably won't use the debugger much, as most of the time inserting a couple of debugging console logs will give you a good idea of what is going on. But if you still cannot see what is going on after trying to output log messages, it's good to know that the debugger is there to help.
Running your app using the debugger is much the same as running the app on a device. The difference is that the debugger is accessed from the debugger icon on the run toolbar.