I've been playing around with Tunisian crochet and have found that my favourite stitch, so far, is the Tunisian purl stitch. It just looks really neat (and it doesn't seem to curl like the Tunisian Simple Stitch and Tunisian Knit Stitch do).
Here's how I do it:
Start by bringing the yarn in front of the hook:
Then insert the hook into the next vertical bar (just as you would for the simple stitch):
With the thumb of your left hand, hold the working yarn down:
Yarn over by bringing the hook in front of the yarn, then under and behind it:
Start the pull through. When you get to this point, let go with your left thumb:
This part takes good timing. Let go too soon and it's really hard to pull the hook through. Let go too late and you end up with a bigger loop on your hook than you intended, and it makes your gauge go all wacky.
Finish pulling through to add the loop to your hook:
This fabric was made by alternating two rows of Tunisian Simple Stitch and two rows of Tunisian Purl Stitch: