Practice overcoming hunger as preparation for a fast

Condition yourself to eat at different times of the day.
For example, have lunch some days at 1 pm, and other days at 2 pm or 3 pm. When you follow a strict eating routine, you will start to feel hungry at particular times as you are used to eating at those times - this can easily ruin your fast.

Break your associations between food and other activities.
For example, watch movies without eating popcorn or sipping on sugary drinks. Or, attend fun events without eating anything at the venue.

Learn to eat only at the table.
This will help discipline you to not eat in odd places and at odd times. For example, when you are used to eating only at the table, you will start finding it hard to eat in other places such as your car, your couch, your bed, or at the lecture hall, no matter how hungry you are.