Step 1: Things you need
You can use any size or kinds of plastic bag, with or without print.
Make sure the plastic bag you will use is clean.
Step 2: Cut the handle and the end
So you will have a turbular plastic.
Step 3: Cut to pieces
You can cut it 1 - 5cm wide, depends on how thick you want your plastic yarn will be.
Step 4: Start connecting
1. Put your plastic piece overlapping one and another
2. Fold one piece and slide it under
3. Pull both piece gently untill both piece are connected
Step 5: Make a strand
If you run out of yarn you can repeat step 1 with a new plastic bag.
Combining different plastic bag is a good idea to make patterns.