I'm much better at signing my samplers than I am my quilts, still they are not all signed.
The easiest way is to add initials and/or the date into the sampler.
I prefer to use all 3 initials, but sometimes, for design reasons or to fill the available space I'll only use 2 initials. No matter how I stitch it, M always takes up space.
Sometimes I even have to go over one or backstitch.
I have finished many samplers by adding a quilted border. Then they will have the details magic markered on the back. These won't be washed so I don't need to worry about the marks disappearing.