The 'right side' is the side that's worn to the outside, the 'wrong side' is worn facing the body. For patterns like scarves and sts like garter st, either side can be RS/WS. For stockinette st pattern (knit one row, purl the next) the knit side is considered the RS. If you go to the Tips page and scroll about halfway down to the Duplicate Stitch Join under Joining a new Color, the video shows how to weave in ends over existing sts so they won't show.
sue- knitting heretic