My go-to needle is a 80/12. That's usually where I start unless I'm sewing on denim or something equally heavy. I have used a 70/10 for silk and finer fabrics.
Stitchnripper, I don't know why you would use an embroidery needle. I do use microtex needles which were recommended to me when I bought my Bernina. They are very sharp and (as I remember) somewhat like an embroidery needle. I use embroidery needles but only when I'm using rayon or other decorative threads. I"m not sure what the advantage of an embroidery needle over a microtex would be. Did she elaborate?