Maya, I agree with everyone else that the best thing you can do for dry hair is to stop using sulfates. They are horribly drying lathering agents, not put in products for cleansing but rather for that "sudsy clean" feeling that consumers like. When I stopped using them a few years ago, my hair became exponentially softer over the next three months or so.
You've got a lot of good advice regarding this, but I'll add my 0.02. There are two main ways to go sulfate free. 1) Use an organic shampoo that doesn't contain them (ie. sodium lauryl sulfate and sodium laureth sulfate won't be in the ingredients list). 2) "Wash" your hair using a thin, cheap-ish conditioner and lots of friction. Products like WEN are basically souped-up versions of the latter, cleansing conditioners which contain no sulfates but are designed to be used like shampoo.
If you're going to try this, one of the most important things to remember is to stay away from silicones. Most silicones are not water soluble, so without using foaming sulfates to remove them, will build up in your hair, making it limp and dryer in the long term. Look for anything ending in "-cone" or "-xane" in the ingredients list. Certain brands like Pantene are notorious for using loads of silicones, and others like Suave have a lot of products without them. The good thing about conditioner washing is that the best products for it tend to be simpler and cheaper.
You might find that you still want to use a sulfate shampoo once or twice a week to deep-clean, especially as you get used to this. Sodium laureth sulfate is less harsh than sodium lauryl sulfate, so maybe look for a mild shampoo with that in the ingredients list.
