FORGETTING PROTECTION. Not enough people use thermal protectors. Look for a no-hold formula
RUNNING OVER (AND OVER AND OVER) CURLS. Get hair as straight as possible before ironing by stretching out each section with a brush. Then slide the iron slowly and steadily in a single pass. Don't stop and go, or you'll get horizontal lines.
GOING BOARD-STRAIGHT. Instead of ironing hair straight, parallel to your face, move your arm in a C shape as you proceed down the hair, and bend the ends under.
IRONING DAMP HAIR. If you hear a sizzling sound or see steam, well...it ain't good.
THINKING BIGGER IS BETTER. Hulking irons make it hard to get to the hairline where hair tends to be curliest. Instead choose a straigntener with ceramic or tourmaline plates that are an inch wide.