Step 15 - Ask your hairdresser to be kind to your hair.
Do have a trim every 3 months to keep split-ends in check, but don't let the hairdresser loose on your hair with overly hot water or with a set-to-hot hairdryer or (even worse) boiling-hot straighteners.
Ask for the hair-washing water to be set to warm (not hot), then request the blow-dry temperature is turned down to warm too. Your hairdresser won't love you for this request, as drying your hair will take twice as long, but at least your hair won't end up being re-frazzled and re-damaged every three months.
Better (and cheaper) still, go to the hairdressers with freshly washed-at-home hair. Then you can ask for a 'dry cut' i.e. your hair is just misted with a spray bottle rather than washed, ready for cutting.