For this technique you will need the following: anywhere hole punch with three or more sized hole punches, a hard surface to punch on, a hammer, a piece of cardstock and a constrasting piece of cardstock or paper, an adhesive eraser, a pencil and eraser, adhesive. You probably have an anywhere hole punch in your tool arsenal from the days when eyelets were all the rage and before there was the Cropadile. My set is from Making Memories and it came with three interchangeable heads in different sizes. You will also probably want to have a tool for poking out the pieces of paper that get into the punch heads. You can use a piercing tool if you have one.
On your cardstock you will need to draw some wavy lines or whatever design you would prefer. Make sure the lines are quite faint because you will want to erase them at the end. Then place your cardstock on a hard surface for punching.
Line up the hole punch along the line next to the first hole. Make sure they are one or two millimeters apart because the hole will spread slightly when it is punched and you don't want to punch into the existing hole.
Continue along in this manner, varying the size of the hole punch as you "trace over" the line you've drawn. The pattern you lay down is completely up to you - do whatever looks good to you. I tend to not use the same size punch for more than three holes in a row. As you go along remember to periodically clean out the heads of the hole punches or the paper will get compacted up inside them and will be difficult to remove.
When you are finished you will have "drawn" your lines with the hole punches, giving you a nice pattern to use on a card. When you have punched all the holes, you can go back over your pencil lines with an eraser to remove them.
You may be wondering why I don't draw the lines on the back of the card so I don't have to worry about erasing the pencil lines. While you can do this, I personally don't like the look of the punched holes from the back. They tend to bevel a bit and the back isn't as smooth in appearance as the front.
Adhere your punched cardstock over a contrasting piece of paper so the other cardstock shows through the holes and you're done! Some nice ways to use this technique are as stems for flowers or strings for balloons. You can also use it to write out words. You could use just one size of punch for a different look as well.