Van - You must be about my height and build. I can lose 19lbs in 5 weeks (but never do it now, for health reasons.) It's tough but, if your target is a big event or something ... I last did it for my wedding.
First, accept that you will be hungry. You'll have to drink a lot of water to make yourself feel 'full'. Doesn't work, but it helps! The water will bump your weight up, so go by your body shape and size rather than your weight. I also used breathing exercises to control my temper; I'm a bastard when I'm hungry 
Next - exercise a lot. I did at least 2 hours a day: one full hour on weights and cross-trainers at the gym, plus an hour swimming or running. Do isometrics while you're watching telly (if you get enough time for that!) and while waiting for buses, etc. Exercise speeds up your metabolism - well, not exactly, but that'll do - such that you burn more energy while not exercising as well as what the calorie counter in the gym says.
Diet - standard low-calorie diet. Eat huge amounts of leafy veg, as they are mostly water and good for you. Cut as much sugar as possible out of your diet. Grill or bake your meat, without fats - but don't cut out fat entirely or you'll get metabolic imbalances with all that exercise. Have baked potatoes with some butter or cheese, that sort of thing. Make as much of your food 'whole' as possible, it uses more energy to digest and is better for you. You must have carbs before and after your workout. I ate a banana on the way to the gym and a yoghurt when I came out. Take a daily multi-vitamin & mineral supp.
You can't keep this up long-term, by the way, without damaging yourself. After your target date, you should gain some weight but, if you keep exercising (maybe 1 hour instead of 2) and stay off the sugar, you will be toned & slim for as long as you like :)
We all have a 'natural comfy' weight and a 'natural healthy low' weight. It varies from one person to the next, but I'm guessing yours are similar to mine. My wedding weight was 128lb; afterwards I stabilised at 139lb then, back to normal life, settled around 149lb with half an hour to an hour of deliberate exercise and normal healthy eating. The reason I've gained weight now is that I'm too unwell to exercise.
If you're quite unfit at present, swap the gym for a yoga or Pilates class and walk or swim instead of running. Dancing's brilliant exercise, so do it whenever you can!