Its so easy to grab a handful of food and eat your entire handful...and then of course sticking your hand in again for more!
What I decided to do recently is to count exactly how many pieces of food I take. Pick two numbers, one bigger and one smaller and use that depending on the size of the snack.
For example, if its crunchy chips or crackers, I give myself 7. I eat it slowly and actually taste the food, instead of eating without noticing how much. When you know you have a limit, you eat slower as well, so you feel full a bit faster.
For a bigger food, like oreos or something similar, I use the number 3. It could be less but if you feel like your not really getting anything, you will most likely eat more later.
Anyway, hope this helps! Pick a number~ lets do this!!