Hi, if I have got it right the link below should take you to the Missourri patchwork Pinwheel tutorial...this is definatly the easiest way to cut a pinwheel, but there are somethings that I think are real important
1. You have be really accurate with your cutting
2. Make sure your seams are exact
3. Cut the diagonals exact
4. Press seams to set...this seems to stop the squares going wonky but I dont know why...
5. Place the light side on the ironing board facing you and press the seem to the darker side.
It is important just to press and not iron otherwise that will distort it.
Then follow how they sew it in the tutorial and you should get really good points.
Mine were really lowsy until I watched that tutorial ( courtesy of someone else posting it on the board)
I think the important thing with pinwheels is accuracy.
I have just sandwiched the pinwheel baby quilt I made on the weekend....when I have quilted it I'll put a picture on the board
Good luck and let us know how you get on.