I say forget the slimfast and get some musclemilk and ON Whey gold standard. One serving of the whey and half serving of musclemillk in water is great. Cheaper and more filling. www.supplementwarehouse.com
Whatever works for you. Whether that is Slimfast, just "cleaning your diet"... there was a recent study that showed 1) all weight loss plans work about the same 2) most people gain the weight back.
The reason being as soon as you go off the Slimfast or NutriSystem or whatever you go back to your normal pre-diet routine. If you learn proper nutrition then it will stay for a lifetime.
If you stick with Slimfast... use the optima shakes
Breakfast: Optima Shake
Snack: piece of fruit and energy bar (you can use the Slimfast ones or one of the other varieties)
Lunch: Optima Shake and 1/2 a sandwich (turkey or chicken, skip the mayo, add some lettuce)
Snack: piece of fruit and energy bar
Dinner: chicken or turkey or fish, some veggies.
Snack: piece of fruit
Two of the shakes per day will give you just about all the vitamins and minerals your body needs. The rest will be taken care of in the diet. The shakes are just under 30% fat but they are high in sugar.
Other than diet aim to do 30-60 minutes of activity a day (walking is fine).
Eat lots of little meals. Grain cereals, smoked turkey, grilled skinless chicken, fruit, veggies, etc. Drink lots of water. With meals, without meals. Drink that water.
Cut out as much of the beer as possible. Stay away from the "white devil" - sugar. Candies, cookies, sodas, etc. And try to never eat any kind of real meal after 7 pm.
Then start cardio exercises to light up your metabolism and after a couple of weeks you'll start dropping weight.