Things You'll Need
pen (or computer images & printer)
Draw or write something on a piece of paper or print out an image at about 100x100 pixels. Cut the image out along with a sheet of cardboard the same size and glue them together.
Yup, that's it. Dang, I made a bunch o' those. I usually put a character portrait on one side and wrote the character's name, class, and level on the back. I also made some quicker and dirtier versions using two pieces of paper taped to a nickel. The extra weight of the cardboard or nickel is necessary so that pieces don't go flying all over when someone opens up a book or if you turn on a fan or whatever.
Other Ideas for Quick Counters:
-spare change (good w/ few characters and limited enemy types)
-Go stones (without or without masking tape and Sharpie for names)
-Scrabble or Bananagrams tiles
-if you have enough of particular colors, use dice!
What other things have you resorted to using as counters in a game? If you have any favorites or any stories about counters in general, let me know in the comments.