Just the regular k2tog or ssk decs will create a spiral when they're done every other round and over the previous one. I'm sure there's books for general knitting designing. Maria Righetti has one for sweaters, but I think she also has another one. Barbara Walker's Knitting from the top is aimed mostly at top down knitting, but not just for sweaters, she covers other items. And Elizabeth Zimmermann wrote a lot of knitting books that contain recipe style patterns, but they contain a lot of information about how knitting works. You can probably get hold of these through your library (they can request them from others) so you don't have to go buy a bunch.
sue- knitting heretic