Choosing the right conditioner for your hair is, again, depending on your hair type. If it's dry, the way to apply the conditioner on your hair, on long hair, would be to start mainly at the bottom, putting the products into your hand, and then slightly make your way up. Do not put conditioner on the roots. If you do that, you will make your hair flat or maybe greasy. Make sure you rinse your conditioner well enough, so it doesn't get dirty looking and also weighing your hair down.
If you have dry, really dry hair, there is definitely some deep treatment conditioning that you can do at home. Take a hot towel, wrap it around your hair. Let it sit for half an hour. It will work your hair and make it much more healthier.
Like I said, there is no rule to getting conditioner. Make sure, if you have colored hair, that it's a conditioner for colored hair. The more you try it, the more you will find the perfect and the right one for you. Like the shampoo, you need to have two or three conditioners in your bathroom, so you can actually use one on one day, and the next one the next day, so your hair won't get used to one product.