When submitting a bug report, it is very important to be as specific as possible. Simply stating "it doesn't work", or "the app crashes" is not useful. Please provide the full specifications of your device (at least specify the make and model if you aren't sure about the rest), which version of Android or ROM/OS your phone is running (if known), which version of the app you are running (if known), and which plug-ins and settings were selected (if applicable). After that, provide a detailed, step-by-step set of actions that can be followed to reproduce the bug.
Be sure to think about the bug and search the forums a bit to decide whether it is a compatibility issue (many problems are game/plug-in specific, and should be posted in the "Compatibility Discussions" board), or if it should be posted here (if you aren't sure, just post it here). If another person has reported the same bug, please add your report to their thread, rather than starting a new topic (it keeps things more organized that way).
A proper bug report might look like this:
Device: Packard Bell Liberty Tab G100
CPU: Nvidia Tegra 2 (T20)
RAM: 1 GB
Rom: HC 3.2, rooted, @1544 - 1680 MHz
App Version: Current market release
Description: When I start the app for the first time and open a ROM, the wrong virtual gamepad layout is displayed. If I exit the game to the main menu and then enter the Virtual Gamepad Settings screen, it shows the correct layout under "Change". If I then go back (without choosing a skin from the list) and resume the game, the correct layout is displayed.