There's a couple ways to do it - with purls on the WS or aslo repeating the yo k2tog pattern on the WS. The lace pattern will add only 1 stitch on the row that it's done, but to make a triangle you need 1 inc on every row or 2 on every other one. So if you do a purl row, you would have to do a YO at the beg of it.
Play around with both ideas and see how you like it. I know there's several basic shawl recipes that would work, but I can't recall where to find them. I'll try to look and see if I have a copy of one and let you know.
sue- knitting heretic