moroccan oil is great, pricey buy worth it! you can use this with loreal mystic oil. Also use a deep conditioner / leave in conditioner. Don't wash your hair everyday as this also dries it out. use a heat protection if using straighteners.
My hair was pretty fried after a couple of colouring mishaps and general wear and tear from my hairdryer etc. (I don't really straighten it or anything.)
I wanted to try and keep as much length as possible (which is not a lot as I have very short hair!) but I knew the ends had to go, so I had a trim but I didn't cut all the split ends, just most of it, and I'll have to go back and get a little bit more off etc. etc.
My best recommendation however is Retread conditioner from Lush. It's quite expensive compared to most high-street products at about £9.50 a tub but I love it. It's their thickest, heavy duty conditioner and you can use it like a hair mask as well. For me it's pretty good value for money as I have pretty short hair in like a pixie crop so if you've got really long hair then it might be a bit too pricey! You could always get some just for your ends though.
They also do a shampoo called Rehab, designed to be used with Retread, specifically for damaged hair. Rehab smells of peppermint, it lathers really well (I know some people find Lush stuff doesn't lather enough) and it's got enzymes in apparently to improve your hair's condition.
Hair oils are really good, you can get Moroccan Oil which is really expensive, but a great cheap alternative is coconut oil. It's a solid, so you melt some in your hands, smooth it through your hair before you wash it, leave it in for a few hours (or overnight if you have the patience) and then wash your hair as normal
You can't repair damage hair, you have to chop it off. Your concern is with preventing the damage in the first place. Use heat as minimally as you can. Learn how to dry your hair straight with a hairdryer to avoid straighteners. Always use heat protection spray. Use a quality shampoo and conditioner (try to avoid supermarket buying) and use a good leave in conditioner.
A good hair care brand is Matrix for damaged hair.
Also you can try some oils, my personal favourites are coconut and moroccan.
Do you really need to dye your hair? If you are dying it dark, why not try henna? Lush henna is amazing for conditioning and colouring your hair at the same time.
Argan oil etc are all really good but OH MY GOODNESS so is Olive Oil. Tried it out for the first time today as my hair's been ruined from colouring, blowdrying, straightening etc and the results are amazing! It's softer on the ends, generally feels heaps better and it's even shiny. What's best is it's not greasey! (never had a problem with greasey hair mind you) It's even sprung up into tighter curls again - mum came home from work and immediately commented on how bouncy it looked.
Anyway, what I did was warm up a couple of tablespoons of olive oil in the microwave for a minute and then worked it through my hair with a wide-tooth comb and then ran the remaining oil through with my fingers. Then I tied it up and put a shower cap on and wrapped it up in a towel as well to keep heat in. I kept it on for just under 2 hours and then rinsed it out with a little shampoo and then just conditioned the ends. And voila - soft healthier looking hair!
I'm planning on doing this at least twice a week now as I can't fault it! Also read lots of good reviews on doing this online
The key with hair that is very damaged is (as someone said) to try to cut it off. When hair is breaking off it's structure is destroyed and you can't repair it.
If hair just feels incredibly dry, slightly brittle or matted there is stuff you can do. The only retail treatment I know works well to repair the elastin inside hair is Philip Kingsley Elastizer. It's pricey at £25 but a tub would last a while. You need to make sure you clarify the hair and ideally sit in a hot bath with it on your hair as this will open the cuticles.
Argan Oil is good, but also Coconut oil is one of the few natural properties that has a molecule small enough to enter inside the hair. Many conditioners and treatments will only sit on the hairs surface and not be able to evoke any natural change.
A salon I used to vist (as an educator) many, many years ago sweared by organic tomato juice, Extra Virgin Oil Oil and egg (all mixed up). The stylist did a lot of afro hair and claimed the mixture 'feed' damaged hair. Technically it could do as the tomato juice is acidic and would reduce an alkaline PH (which can typically be the cause for damage). The egg is protein and the Virgin Olive Oil would emulsify the solution into the hair. If you want to try this tip, simply pour all the ingredients into a cleaned out colourant applicator bottle and pour onto hair you have rinsed in bicarb (this keeps the cuticle raised). Wrap the hair in cling film and leave for 30 minutes, then wash out with a gentle shampoo.