Re: unmounting USB stick/external drive
If you write to USB memory or other device it is important to make sure that it is finished writing before physically disconnecting it. If it is something that has automounted it will typically have a little up arrow with line under it to the right of the partition name in file manager. Clicking on that up arrow will umount that partition and usually other partitions on that device. But if you clicked on that device name, it is best to click on something else first (like your home directory) before clicking on the arrow to umount a device.
Hopefully, it will tell you if it is not yet finished writing when you umount it, or if the device has an activity light wait until that stops flickering or goes off and that partition is no longer listed in file manager (or in Unity bar or desktop depending which gui you are using).
If you want to do something like repartition the device, you can use the umount command in a terminal which will umount the partition without actually disabling the device.
i5 650 3.2 GHz, 8 GB, nvidia GTX 750 Ti, 32" 1080p | i7-4700MQ, 8 GB, Intel HD 4600/nvidia GTX 765M, 15.6" 1080p | etc.