Sorry for any awful block-y, line-y pics... my photo uploading never works quite right!
Get a t-shirt, preferrably one a bit too big.
Cut it down the centre, at the front. Make sure its straight and actually in the middle!
Fold over a hem and neatly sew it down, I used back-stitch. Only go up to about half-way...
... and for the other half, fold the hem at an angle like this <-, then carry on sewing the hem up, so you have a v-neck sort of thing
sew a couple of pieces of ribbon onto the front, at the point where the v-neck begins...
Tie them up and then thats it!!
This is the only pic I have of the finished cardi, and it does look a bit odd-shaped on the hanger, but much better when you wear it!
Any questions? Ask! :D