I personally prefer using resistance bands to weights and doing 3 sets of 15 reps. The resistance bands help tone without building muscle bulk.

For cardio, 30 minutes is often recommended and a great way to mix up a workout is to hop on the treadmill for 15 minutes. While on the treadmill, every two minutes hop off and do some leg squats or leg extensions. This not only raises your heart rate, but you are getting a great leg workout too. Then for the last 15 minutes of your cardio, hop on a bike or elliptical machine.

I have found that mixing up my workouts a) helps me from getting bored and b) ensures that I am working different muscles. In addition, my trainer once told me that it is best to do your weight training before your cardio. This gets the muscles warmed up and enables you to burn calories and fat more efficiently.