Well, I have to begin by saying that you either have an hourglass figure or you don't
....for example, I have no hips...lol! I guess what you are trying to get at is how to have long, lean muscles...you just want to tone and not bulk up, right? Cardio is excellent for burning fat, particularly when mixed with weight training. This is the best combination to really increase your metabolism, which is what ultimately allows you to lose fat and keep it off. Now, let's define "light weights" shall we? Too often I see women afraid to lift heavy weights for fear of becoming massive. They end up lifting a weight that is far too light and getting nowhere near the momentary muscle fatigue necessary to build muscle. And when I say build muscle, I don't mean huge muscle mass. Being toned is about having muscles. Simple as that. So, if you want to tone, stick to 12-15 reps with a weight that will take you to momentary muscle failure, that is, a weight with which you would not be able to properly complete 2 or more reps than the prescribed amount. If you could keep going for many more reps easily, the weight is not enough and you WILL NOT get the desired benefits. You MUST overload the muscle to get results. And when the weight becomes too easy as you get stronger, KEEP INCREASING IT. Don't be afraid, as long as you respect the repetition range, you will be fine...even if the weights you are lifting seem like a lot, this does not mean you will "get big".
Pilates is an EXCELLENT complement to a weight training program. It works your core in a very functional way, while helping maintain muscle flexibility. I would definitely recommend it if it is available!
Hope this helps, good luck!!!