Here you go: This is how I do it-
http://www.pacinfo.com/~hallock/triangles.html
Make all the rows before sewing the rows together. I draw the 1/4" seam line on the back of the triangle rows, then match up the seams by putting a pin through the back of one straight through to the point of the triangle on the other row- on that drawn seam line. Seems like a lot of work to some, but it does work. Then I iron the rows out by using Eleanor Burns method shown on her free Merry Go Round (pinwheel) quilt pattern from this site. It is on page 3, #6.
http://www.quiltinaday.com/freepattern/