Weight loss and exersize?

hi im 18 and i weight 11 and a half stone i have put on weight lately a STONE and a half and i want to loose the stone and a half by may this year as i am going on holiday i want to loose the stored fat in my lower stomach ans that area and legs and need a diet that will make me loose weight quiet fast and exercise to go alongside i am the most willing and when i put my mind to it i can do it so any ideas would help ut what i need really is a full diet plan and exercise routine to get rid of stored fat and loose more weight on top of that and then tone up thanks x