I happened to need shims, but didn’t want to spend money on getting a shim. So I decided to make one. My method is taken from separate sources, and then I combined the best ones to make a cheap and reliable shim. Homemade shims can be made quickly, for free, and work just as well as the ones you buy. So how to make it:
Materials: Scissors, Nail Clippers, Hole Punch, Credit Card/ Gift card, or something among those lines.
Step 1: Take the hole punch, and punch a hole in the card. Leave at least 3mm on all sides of the hole.
Step 2: Since the diameter of the hole is a tad small, stick a scissor or knife into the hole, push the card down until it comes into contact with the blade, and twirl it around, scraping the side and enlarging the hole.
Step 3: Use your scissors to cut off most of the card, leaving the hole with around 2mm of plastic around it.
Step 4: Use a nail clipper to finish it up, leaving 1mm or less of plastic around the hole.
Step 5: Insert into the yoyo and play! 
Sources: http://www.theyo.com/yoyo/showthread.php?t=46714
However, in contrast to what the topic says, I use a scissor for making the hole larger, just because it’s easier, and I only use plastic, since I discovered that paper can rip when you twist.
