Paper Clip
When using a paper clip I start out by bending the end away from the paper clip so that it will easily slide into the stitch.
Then slide it into the stitch so that the middle of the paperclip is now around it.
Now fold the end back down, and your stitch marker is secure and you're ready to work!
Safety Pin
I love using a safety pin because it's so simple. Just attach it to the stitch and you're done!
Stud Earring
Using an earring that you'd never wear but are still cute, or maybe one where you'd lost the other, can just be fun to use since it adds a personal touch.
And pretty much any one will work!
Feel free to let me know of any other stitch markers you use!