This is probably the most failure brings head to users of low-end phones.
In my family until recently there were three Samsung Galaxy Young and three phones constantly had the same problem: The memory was full. No matter that borrases applications or photographs, the memory was full and if by some chance the infamous Message disappear this again in a matter of a few hours.
Some things to consider here are:
Not having installed games: These applications often have a large volume of data, and can store much more with later updates. Obviously we are talking about very big games, having the threes not going to happen ... probably.
Clears the cache of your applications: data cache are stored applications. These data, as we use the application, are increasing. As I have explained above, to erase this just have to go to Settings> Applications and select the application you want to clear the cache. Once inside, you will see a button that will give us the option to delete the cache of this application.
The root option: If we rooted our phone we can install applications 2SD link that will allow us to keep all applications to the SD card.