There is a debate, and ppl say, that there's no such thing as "spot" training. for instance,u wanna lose weight in ur thigh area, so u do squats, ppl say that's a myth. In my opinion,it's somewhat n somewhat not true. here's why, if u do squats to lose weight off ur thighs, it might not help you lose weight off your thighs, but it will build muscle in ur thighs, possibly and maybe making ur thighs bigger. BUT at the same time, if you are losing weight by swimming or running, or eating lower calories and eating more healthy....and if u do begin to lose weight and u do lose fat in that area, you thighs will look better since you've been working them out and you've gained muscle in that area to give your thighs a lean look.
But, back to ur question. From what i've read and researched, eating health and doing cardio is the way to go. If you're burning fat through an exercise, your body will search for fat to burn, but you can't choose where it will burn fat from. As time goes by, you will eventually notice your thighs looking slimmer. Remember, to burn 1lb of fat, you must burn 3500 calories. Find out how many calories u need to eat to maintain that weight, subtract 500 from that, and that's how many calories u should eat daily to lose at least 1lb per week.