Step 1: Create the crest using curved lines.
Step 2: Use circles and curved lines to make the jaw.
Step 3: Draw a circle with curved lines to create the eye.
Step 4: Make a small circle for the nostril.
Step 5: Draw a crooked line for the mouth.
Step 6: Use a variety of lines to make the dewlap.
How to Draw an Iguana Face – Step-by-Step Tutorial