It is a uniform diameter hook ended by a sphere.
First row : picking up the loops on the hook. All stitches remain on hook.
Second row : drawing all loops, on the end of the row there is one loop.

(Be indulgent with my tranlation !!!)

French translation

	Basic afghan stitch First row : * Insert hook at front and from right to left around the upright stitch or bar, yarn over, draw loop through and keep on hook, rep from * to *. 2 nd row : do not turn the work, yarn over, pull through 1 loop, * yarn over, pull through 2 loops *, rep from * to *. 3 rd row : like the 1 first row. 4 th row : like the 2 nd row.
	Knitting afghan stitch Make the two first row like basic afghan stitch. 3 rd row : * Insert hook between the two bars of the second vertical chain (as showed in the design), yarn over, draw loop through and keep on hook, rep from * to *. 4 th row : like the 2 nd row.
	Full afghan stitch Make the two first row like basic afghan stitch. 3 rd row : * Insert hook as showed in the first design , yarn over, draw loop through and keep on hook *, rep from * to *. 4 th row : like the 2 nd row. 5 row : to avoid the shift * insert hook as showed in the second design, yarn over, draw loop through and keep on hook *, rep from * to *, at the end of the row insert hook in the last chain.
	Afghan stitch with double stitch First row : * Insert hook at front and from right to left around the upright stitch or bar, yarn over, make one chain, yarn over, draw loop through and keep on hook, rep from * to *. 2 nd row : do not turn the work, yarn over, pull through 1 loop, * yarn over, pull through 2 loops *, rep from * to *.
To increase in afghan stitch At the beginning of the row, insert hook in the first vertical bar, yarn over, draw loop through, then in the second vertical bar, yarn over, draw loop through, continue others stitch normally. At the end of the row, insert hook under the last vertical bar and the bar behind it.
To decrease in afghan stitch At the beginning or at the end of the row, insert hook under two vertical bars, pull up one loop.
Finish of the work * Insert hook under the vertical bar, yarn over, pull through the loop, pull the loop through the first loop *, rep from * to *, there is only one loop on the hook.
You can find the tunisian crochet on : http://busy-fingers.com/ Also in Belgium : Fil de luxe - 61,chaussée de waterloo - 1060 Bruxelles (Saint-Gilles).