A common objects box is just what is sounds like - a box full of common objects. I've tried to scour my old toys (my mom held onto just about everything), garage sales, and toys my son no longer plays with in order to collect up my "common objects". In my box I have: a cup, cell phone (toy), shoes (doll shoes), sunglasses (they were Timothy's), crayon, bowl (toy), spoon (took one from my son before he started to eat solids), sock, play keys, scissors (all plastic kid scissors that barely cut paper much less any fingers), toy car (as real looking as possible), toy airplane (also as real looking as possible), ball, book. Look around your house and you will find a lot of things that can be put into the box. My box is about the size of a shoe box.
I will pull out the box and act very excited about what's in the box. I'll shake the box and point out to the kids all of the noise that it makes. I'll then have the kids request to open the box. This varies with the ability of the child. For a pre-talker, I'll have them "knock knock" on the box (physically knock on the box while I say "knock knock") and when they knock I'll say "open". If the child has learned to knock, then i'll encourage him/her to say "open" after he/she knocks. If the entire word is too much, then a simple "o" will be acceptable. If the child is a talker, then I'd ask for an appropriate utterance like: "open the box please". Once the box has been opened then I'll let the child choose one thing to play with and explore. If the child is a pre-talker I'll tell him/her the name of the object, its purpose, describe what it looks like or how it feels, and let them appropriately use the object (push the car along the ground, bounce the ball, etc). If the child is an early talker, then I try to give him/her time to name the object. I may ask some questions about the object to get the child to start to learn to describe or target any of his/her goals at the time. When it's time to move on, I say "one, two, three, my turn" and take the object and place it in a bag - out of site, out of mind (hopefully). I'll then pull out the box and the entire game is repeated.
How can this be a folder game? Simply print pictures or cut pictures from magazines of real objects and paste them in the folder. Still make the kids go through the ritual of requesting to open the folder and then talk about the object or objects in the folder. You may want to make several folders with only a few objects in each.
How can you use this for older kids? You may want to start teaching kids about grouping objects into categories. You could have an animal folder. Let them explore the animals that you have in your folder. Then ask if they can think of others. If they cannot, then close the folder and have the child try to remember the animals he/she saw in your folder!