Snacks used to be a problem area here.
I say used to because after taking with them about it, we managed to find another system that would work better.
We have always kept a corner of the kitchen just for them and when we moved to this house, it was a priority to have a spot again.
We decided to allow them a deep drawer, and I love that. They have a bird's eye view of everything that is in there, and everything is easy to reach.
We have provided them with 2 pitchers (one is in the fridge) and 6 small size glasses, bowls, plates, utensils (in the stainless steel container in the lower right corner), 4 medium and 4 smaller size (only one shown) see-through sealable containers to store snacks.
So these are the snacks of the week. They can eat as much as they want, but they know that once the bowls are empty, they stay that way until the following wednesday, which is shopping day (and thus filling day :) ) They got caught the first time and ate pretty much everything in the first weekend, and learned the hard way to wait until the next filling day. They have not made this mistake again!
Pea has suggested a checking system where every scoop served gets recorded on a sheet nearby the drawer (cause he felt like he always missed out on certains snacks that were choosen over and over again by his sister). We have not moved that way yet, but probably will at some point. We have thought about having a set of containers for each child, but we rather the concept of sharing and thinking ahead in a group then have something more individualistic (and it kinda worked since Pea's suggestion is heading in that direction!)
They also have some snacks in the fridge: fruits and veggies are an open bar here They can take as many as they want when they want. But yougurt, cheese, homemade stewed fruits are separated in smaller containers for them to use.
I love how this system works. I don't have to check what they eat and how much as I know that if they go over one day, they won't have anyore some days after. I feel it makes them responsible of their choices and they like it.