You should simply get an external HD to store media such as music, photographs and movies tend to occupy the most space with many users. Apple discusses this in three advice letters which I will note below.
However what is occupying the Other space on your HD, this is made up of a variety of data including OS X, other data files from apps you have installed, Apps themselves, your Trash, downloads etc...
If you want to inventory your system then download and install a tool like Disk Inventory. You can find DI at: