I am making a snake cake and I am stumped on how to make the scale look.

You can make very effective fondant scales by using small, tear-drop shaped leaf cutters.
Cut out lots of scales and attach them, slightly over-lapping.
Looks fantastic.

I use any one of my icing tips. Using the back portion ( large opening, not the tip ) at a 45 degree angle, so only 1/2 of the opening is coming in contact with the fondant , I press into the fondant repeatedly. Makes perfect semi circle scales.
I hope this makes any sense

i use the back of a teapspoon!! simply press the tip of the tea spoon into the fondant and it gives you al ovely half moon impression, keep going in rows and you get a lovely scale pattern

I've used the back of an icing tip.

Works great, just impress it into the fondant.

Jen