Mental prep + small victories = momentum.
Create a powerful goal statement and read it daily. Set up small goals up for each day and week and write them down in a journal/log. Go for a "win" each day by trying to accomplish each goal on your list. These two things together will quickly build the unstoppable momentum you need to create fast fat loss success!
1-day "detox" diet.
For one day drink only unsweetened teas and spring water with lots of fresh-squeezed lemon or lime juice in it. Optionally you can also eat a simple raw diet based around fresh, raw, and organic fruits, vegetables, nuts, and seeds. This will detox and re-energize your body while helping to "reset" your metabolism and possible even allowing you to lose a pound or two easily.
Brisk morning exercise.
Get into the habit of doing some brisk exercise first thing each morning, as soon as you get out of bed. 10-20 minutes of light and refreshing exercise is all you need. This will boost your energy naturally, get your metabolism going, and help to set you up mentally for a healthy day.
Paleo-style diet + carb rotation.
Eat a "paleo-style" diet based around lean meats, veggies, nuts, and seeds. Also include some fresh fruit and beans/legumes for tasty hunger-killing fiber. Finally, learn to rotate/cycle starchy carbs (grains, potatoes, rice, etc.) in and out of your diet to keep your metabolism off-balance and burning fat.
Short, intense, interval-based full-body workouts.
Do short (15-30 minutes), intense workouts based around intervals (short bursts of higher-intensity exercise followed by brief periods of active recovery). Do these about 3 times a week to burn tons of fat and create powerful metabolic changes in your body which will strip off the fat and build vital muscle tissue even while you're sleeping!
Take the Big 3 supplements.
Whey protein, omega 3 fats, and a good multivitamin. That's all you really need to lose 10 pounds in a fast and healthy way. These proven and low-cost supplements will cover all your nutritional bases and also make it easier to recover quickly after tough workouts.
Keep it going with expert advice.
You now have a good idea of what you need to do to lose 10 lbs in about 3 to 3 1/2 weeks. But in order to learn all the "secrets" of fast, effective fat loss you should seek advice from a proven fat loss/fitness expert.
There are several good expert-written guides available online that will tell you all you need to know. Here are a couple of the best:
The Truth About Abs