Other than giving up the straighteners? There's not much you can do, invest in a good conditioner, give your hair a conditioning treatment once a week and use a leave in conditioner before you blow dry and strighten. I use the anti-snap shampoo and conditioner range from redken i think, and it's helped. I can literally snap off the ends of my hair and once a whole highlight snapped off but all you can do is condition. also try only using the strighteners at the ends of your hair - unless you have very curly hair of course, if it's just a bit wavy like mine you can probably get away with straghtening from halfway down - or have day straighteneing then a day not, i try and only straighten mine two or three times a week.