How to Set the default storage of apps in my samsung galaxy young? I have a samsung galaxy young. How can I Set The Default Storage of my apps from Internal memory to SD card. I can't Download Anything right now. Can you tell me how?
You first priority is probably to clean-up downloaded files, cached files, old APF (installation) files to give yourself more room and operate more efficiently.   You can clear cache individual applications through settings > applications > clear cache. 

Use any File Explorer to remove files no longer needed or no longer wanted from your
downloads.  Each browser normally has its own downloads folder.  "SD Maid" includes a File Explorer if you don't already have a separate application.

You can clear cache files much quicker by installing 

"Clean Master"


get rid of "Junk Files" such as cached files


"SD Maid".  Some items within  are  


"Overview"  help to see what you are working with.
"CorpsleFinder"  find and delete files SD Maid believes belong to your old/deleted applications
"AppCleaner"  is a premium feature so you can use "Clean Master" to get rid of cached files, would need to mount your removable SD card, and once mounted, you would have to unmount the card before you physically  remove your card.
Settings > Storage > External SD Card > Mount/Unmount SD card.


You have to set default storage individually per application.  Some applications would slow down everything if they used your removable SD Card storage, such as "play store", and applications that start at startup.

To move an application to your SD card:
Settings > Applications > choose application > "Move to SD card"

To choose applications:
Settings > Applications > on SD card

http://www.tomshardware.com/faq/id-1772970/set-default-download-location-card.html
http://forums.androidcentral.com/t-mobile-galaxy-s-ii/137116-can-i-set-external-sd-card-default-media-storage.html