Replying to Work..kinda need some advice

So i'm a senior in high school and after a shitting turn of events, in November, lost my job working at a ski shop.  I have been searching for a job since December and no luck so far.  I have applied to a total of 15 places, but still no luck.  For info purposes: i apply, then call back a couple days later to make a good impression, asking if they need any more information for my application, and sometimes i call again to just keep my name fresh in their heads.  I know that everyone else is struggling for a job in this economy but a little advice would be greatly appreciated.  Any tips on applying? any tips on what jobs to apply to?I'm open to anything..thanks