First off, make sure that any user media (photos, video, music etc) are stored on the external microSD card. Use the pre-installed File Commander app to move folders if necessary.
Next, go to Settings/Apps/All and check each app for the option to Move to SD card. If this is available for the app use it; it won't move the actual APK only the app data, but especially for large games this can free up lots of space on the internal storage.