Currently work-in-progress, more questions/answers to come
Q: I can't save my game on Android (File I/O Error, etc.)
A: On many newer phones/tablets running Android 3.0+, you'll have multiple storage devices available like internal flash memory and SD card slots (paths like /mnt/sdcard and /mnt/sdcard-ext). Unfortunately, the OS may only permit 3rd-party apps write-access to one of these devices so saves will fail if using the read-only device. Try moving your games to each storage device until you can save without an error.
Q: I can't save my game on iOS (File I/O Error, etc.)
A: Your game directory or save files have read-only file permissions prevent the app from modifying them. Use SSH or iFile to add write access or change the file owner to "mobile". The exact command when logged in via SSH is "chown mobile MyGame.sav", or for a whole directory "chown -R mobile MyGamesFolder/" (replace MyGame.sav and MyGamesFolder with your own filenames).
Q: I can't save my game on WebOS (File I/O Error, etc.)
A: You're using a broken OTA update of WebOS 1.4.5 and the app cannot modify any files in /media/internal. There are some workarounds if you use Preware, but the clean way to solve this problem is to use WebOS doctor and re-install the OS (make sure to back-up and important data beforehand).
Q: I tried to copy a new SRAM/battery save file (.sav, .srm, etc.) but the game still shows the old save contents.
A: When using auto-save states (the default) on most systems, SRAM is usually loaded from the state itself. As a result, you should temporarily disable auto-save states under the system options or delete the auto-save state file as you replace the SRAM file. Once the game performs a clean boot from the beginning your new save contents should appear.
Q: How can I fast-forward the emulation?
A: There are touch-screen and hardware key methods to enable fast-forward (actual speed depends on how fast your device can run the system, up to 4x):
Options -> Input -> On-screen Config -> Fast-forward (sets a screen corner to toggle it, use top-left to avoid conflicts with the default control setup)
Options -> Input -> Key Config -> In-game Actions -> Fast-forward (if using in-app Bluetooth support, use that device's Key Config)