On earthenware bisque, I use underglaze pencil on the side of the piece with a coat of clear over it. I'll put my full surname on pieces large enough to fit it, McG on smaller stuff. Assuming most people are right-handed, I sign on the side of a mug they will see most often.
On leatherhard stoneware, use a regular pencil to incise the signature, again up the side of the piece. A pencil makes a deeper, easier-to-control-and-see, mark than the cheesy little line of the needle tool. Break off any burrs when it gets dry. If you glaze too thick, finger-wipe over it.
My first teacher had us do the humble potter thing; sign the bottom with name of maker and name of kiln. My second teacher said, 'screw that, I'm an artist, I'll sign up the side' or words to that effect (hi, Curtis).
I quit dating things way too many years ago (lots of juried shows had 'made in the last two years' conditions which were annoying) and now that I'm involved in a retrospective project (hi, Gail), I'm suffering for it, triangulating among old installation shots of shows in the '90s to figure out when things were made.
Now that I think of it, I should have used a personal numbering system, useful to me, obscure to anyone I don't tell about it, e.g. year one=first clay class (1972) and so on. Drat, good idea, 40 years too late.