Here are Some of the very Common Food Practices we are doing without any second thought assuming them to be useful or atleast not considering it harmful...

Skipping Breakfasts:
It is very common now a days ...
BUT.....

Breakfast eaters get more fiber, calcium, and other micronutrients than skippers do.
Breakfast eaters were approximately 30 percent less likely to be overweight or obese.

Considering Dinners as heavy Meals: 
Thinking that not had proper meals since morning....
BUT 

Binging or overeating on one time especially at night always slows down your metabolism &  leads to obesity..
Eat light and salt free dinners to avoid water retention in the body.
Eat early enough to ensure food will completely digest before sleep.
Make 5-6 meal patterns, take small portion of food after every 2 hours.

Sip of Tea/ Coffee with Stuffed Paranthas [methi, muli, spinach, gobhi etc.] or Chapattis or sprouts chat & poha etc esp. in winters...
BUT

Tea n coffee hinders to absorb the nutrients esp. calcium & iron in the body.
Try to have milk or if want to have tea /coffee along with your breakfast take it after 15-20 minutes of your breakfast.

Drinking carbonated drinks with lunch and dinners, especially during outings:
BUT

Increased consumption of soft drinks is associated with increased energy intake. 
The body doesnt seem to "register" fluid calories as carefully as it does those from solid food. As a result they are added on top of the existing calories from the rest of the diet. 

Walking immediately after taking dinners:
BUT

Immediate walk after dinners may lead to abdominal cramps or other digestive problems.
Always wait for 15- 20 minutes after having your dinners.

Juices intakes as compared to Whole Fruits:
BUT

Fruits are high in fibers as compared to Juices that is considered to be very good for the health benefits.

Eating fruits immediately after taking meals:
BUT

Eating a fruit after a meal is not recommended, because that is overloading in terms of calories intake 
Sometime mixing of fruits with food produces gas which can give discomfort.