Place this sign then right click it! What happens?
/give @p sign 1 0 {BlockEntityTag:{Text1:"{text:\"Click Here\",color:\"red\",italic:true,underlined:true,clickEvent:{action:\"run_command\",value:\"setblock ~ ~1 ~ diamond_block\"}}",Text2:"{text:\"For The\",color:\"gold\"}",Text3:"{text:\"Best Thing\",color:\"green\"}",Text4:"{text:\"EVER\",color:\"blue\",bold:true}"},display:{Name:"Custom Sign"}}