Here's the structure of the /setblock command:  
/setblock x y z block data method dataTag

xyz are the coordinates of the block  
block is the TileID of the block (includes id:0 now!)  
data is the block data (i.e. 5:1 spruce wood)  
method is one of three things: keep, replace, or delete  
-Keep spawns the block at the coordinates.  
-Replace replaces the block at the coordinates with the block ID.  
-Delete removes the block at the coordinates and then spawns the new one in  
dataTag is tile entity data.  

From Minecraft wiki