I have done it three different ways:
I have made my own cutting 2 1/2 inch strips, and ironing with the Simplicity binding maker. That's what I do now, and love it.
I have bought binding on ebay for .40 cents a yard.
I have bought bias tape (pre-made) from Walmart, but they never have enough packages or the right colors. However, it sure is fast to use...
What about you? What do you do about binding?