Should you sign and date your work? If it is intended to be entered in a competition, possibly not. Find out the rules first. Otherwise, go for it! Be proud of your skill. Signing can make a piece more valuable, as the years go by.
Samplers usually incorporate the stitcher's initials and the year into the design. All other designs require a little more creativity on the signer's part.
Some people use permanent ink and sign on the edge, where it will be hidden by the mat or frame. Personally, why would you want to hide this interesting and valuable information?
Some people find a way to stitch their name/date with teeny letters, over one or two threads. Try out some variations on scrap cloth, until you find a look you like.
Don't abbreviate the year. Stitch "2000" rather than "'00." Your stitching may survive you by many years, and even though you may think the project is unimportant, later generations may disagree.
There are several things you can do to make a signature visible but unobtrusive. For example, use a thread colour that is only a shade or two darker than the fabric. Or incorporate the signature into a shadow, using the shadow's colour. Or put it below an object, using the object's colour. Or figure out a way to make it part of the design...