I actually disagree a little bit with the weight training thing being the most important, to an extent. To be most effective, you must do both cardio and weight training. Why? You want to both burn fat and build muscle at the same time, not build muscle and take fat off later, which is considerably more difficult to do.
So.. I recommend that you do circuit training
, which is essentially both. Do a few minutes of cardio and follow that up by a few minutes of strength training with weights, focusing on different areas of the body, and then go back and forth. When you do your training with the weights, also make sure to incorporate other parts of the body. For example: Instead of just doing arm curls, why not add a lunge with those arm curls? You'll burn more calories and you'll work the muscles in your legs in addition to the muscles in your arms.
If you spend at least 30 minutes everyday doing something like this, you'll be in pretty amazing shape. For help getting used to the idea of circuit training, I'd suggest getting Jillian Michaels' 30 Day Shred or her Ultimate Body Make Over. The 30 Day Shred is three, 25 minute workouts, of different levels - all circuit training. The ultimate body make over is two videos - one to burn fat and boost metabolism, and the other to work out different muscles of the body. These are both about an hour long, but let me tell you.. you absolutely cannot go wrong with either set of videos. She used to be overweight, so she knows what works.. and.. they can be hard, but it is so worth it. She's cut pretty well, and all the people she's trained end up looking quite nicely toned [or well on their way to it] once she's through with them.
And, in general, I would also recommend Pilates.
Anyway -- Stay hydrated. Drink as much water as you can because it will keep you feeling good throughout an intense workout, it helps flush out your system and it's just good if you want to stay in shape. I would stay away from soda, sugary juices and other sorts of drinks like that. They'll only hurt you in the long run.
Caloric management is important, but a caloric routine, of course, varies from person to person. I would highly advise talking to a nutritionist before jumping into the calorie-thing. Because, honestly, what works for one person may not work for another person. With all due respect to the poster who gave you that advice, you have a different body and you will ultimately have a different work out than she does. I mean.. if your body isn't used to working out so intensely, you may burn more calories which means you may need to ingest more calories to stay energized. Or maybe you'll need to take in LESS calories per day. It really varies from person to person, so I advise talking to a doctor before engaging in something that might do your body more harm than good.