how do i make a ruffled edge on the end of a scarf?

Ruffled as in wavy/gathered sort of effect?

Just increase 1-2 stitches in every stitch across the row.
Now do this for either every row or every other row until you're satisfied with the ruffle.

Then bind off.

Hope this helps,
Dot

I've made this scarf several times and I think the ruffles look pretty good

http://www.mistialpaca.com/downloads/ribs_ruffles_scarf.pdf