I need an effective, short-term weight loss and toning plan

I am 18-years-old and I am determined to lose a few pounds and tone my body by the end of May. I just began running and I'm starting off by running a mile and hope to work up to a 4-mile run 4 or 5 days a week. My diet is generally a bowl of cereal in the morning, and a turkey or ham sandwich with some type of fruit and a bottle of water. Dinner is something different every day, but usually healthy. I also have been doing an ab workout for about 7 minutes after I run. Is what I'm doing effective? What are your suggestions?

Thanks!
*Annie*