Duplicate stitch is a versatile way of adding color to a project. It can be done on the knit side of Stockinette Stitch fabric and forms Vs over the stitches that "duplicate" the stitch that is already there.
You can use charts to add duplicate stitch to your knitting or just stitch freehand whatever sort of shape you want. It works particularly well for rather small areas of detail, as it adds thickness and rigidity to a knit piece.
To start, decide where you want your stitching to begin and bring the point of a needle threaded with yarn up through the point of the V in the first stitch you want to duplicate. Pull the yarn through. Leave a few inches of yarn at the back of the work to weave in later.