Worsted weight yarn (if you're just trying this out for the first time, use some easy and cheap stuff, like Red Heart. It took me a few tries to get this stitch right, and kind of ruined some of my fancier yarn)
Size H hook
Sl st: slip stitch
Dc: double crochet
1. Ch 30. Sl st into the first ch, so you have a circle and be sure not to twist your chain.
2. Ch 3, dc in the same st with the sl st. Ch 2 and skip the next 2 sts. (2dc, ch 2, skip 2 sts) 9 times. Make a sl st into the first bar (the ch 3 from the beginning of this row). You should now have 10 sets of 2dcs.
3. Ch 3, turn your work to the side. 5dc into the SIDE of the ch 3 of the previous row.
Ch 1, and turn your work 180 degrees. Make 5dc in the side of the first dc from the previous row.
Skip the next 2dc section, and crochet 5dc in the side of the next dc, ch 1, 5dc in the second dc of that section. Continue around, until you have 5 crocodile scales. Make a sl st in the bottom dc of the first scale. Ch 2, and make a sl st in the last 2dc section that doesn't have a crocodile scale in it.
I know it seems like a daunting task, but once I spent about an hour messing with this stitch, it became super easy. If you have any problems, I'd recommend checking out this lovely lady's blog: http://yarn-muse.blogspot.com/2011/01/crocodile-stitch.html. That's how I learned the stitch.