Preparing plastic bags is pretty simple.
Start with a plastic bag.
Fold it in half.
Fold it in half several more times.
Cut the handles off.
Cut the bottom off.
Cut the bag into about one-inch strips.
You should end up with about 10 pieces per bag.
Unfold 2 pieces and loop them together.
Loop all the bag pieces together to form a chain.
Roll the plastic bag chain into a ball.
I typically wait until I have a lot of bags. Then I cut them all up and end up with a crazy mess like this. Then I roll this mess into several large balls.
I like finding yarn at garage sales and thrift stores. I especially like really old yarn that was probably sitting in some old lady's closet for several decades. It makes me happy that someone probably bought the yarn with a specific project in mind, never got around to doing it (but thought they would, so kept it around forever just in case), finally got rid of the yarn, and now I'm able to put it to good use.
Here are some things I made with this yarn:
White Bags -- HEB
Brown Bags -- Fiesta, Central Market, Whole Foods, and Wheatsville
Brown bags -- HEB
Green bags -- HEB in Mexico
Yellow and Blue bags -- Various places in Mexico
White Bags -- HEB and various other stores
Colored Bags -- various gift bags
Colored Bags -- collected on the streets of Monterrey and Tampico
Yellow bottom -- Best Buy and American Statesman
A little bit of everything