What's a crocheter to do?
The purpose of stitch markers is to mark particular stitches so that you can come back to them later in the pattern. They sell fancy ones on Etsy and in craft stores, which are fun to collect and pretty to see hanging off your work.
But if you don't happen to have any of those laying around, you can also use safety pins to mark your stitches.
In a pinch, especially when crocheting on the road, The Animator's Wife has been known to whip out an earring and use it to mark stitches.
So really, pretty much anything can be used as a stitch marker, as long as it won't get in your way and can be easily removed later in the project.