Avoid high-calorie, high-fat foods, easier said than done I know!  (I struggle with this, also.)  Don't give-up on pop/soda, chocolate, ice cream, etc., but just eat those foods in small portions.  For instance, I consume mostly water at 0 degrees Celsius (which I mentioned in my other post.)  I do this by taking standard tap water, and then putting it into the freezer.  After 20 minutes or so, ice will have formed on the top, and when that happens, the rest of the water below is near freezing.  Consuming cold water instead of pop, juice, milk, etc., will give you a negative return on calories.  The water, of course, has no calories, but the coldness of the water will expend calories heating it up to 37.5 degrees Celsius, which is the temperature of your body.  Just be careful about drinking too much water; you may be emptying too many "heavy metals" from your body, and it can also kill you:

http://www.scientificamerican.com/article.cfm?id=strange-but-true-drinking-too-much-water-can-kill
http://en.wikipedia.org/wiki/Water_intoxication

The upper limit, if Wikipedia is correct, is 1 to 2 liters a day, with another sources recommending "2.7 liters or 91 ounces for women, and 3.7 liters or 125 ounces for men spread throughout the day."  Remember, a pound of body fat is 3500 food calories, so it will take time to lose weight -- eat low calorie foods, avoid high calorie ones, stay active, and drink cold water, but just do not overdue it.  My "cold-water therapy" will, at most, expend 100 calories per day, the same that you would expend from walking 1 to 2 miles.

I wouldn't worry about it; it isn't so much how many liters of water you drink per day as how fast you drink it.  Just stay under 5 liters per day and you should be fine, but keep it cold!