The right amount, and what to get

To start off: Don't trust that 2 in 1 bull-shiza. All it does is dry out and damage your hair! Use shampoo and conditioner! Not at the same time! Okay back to topic now (lol) ...

If you shampoo every other day and condition everyday, when your conditioner bottle is empty, you'll notice your shampoo bottle is about half full! What you need to do is this: don't buy the same amount of each. If the shampoo bottle and conditioner bottle you get are the same size, get one bottle of shampoo and two bottles of conditioners. Another alternative is buy a small shampoo of let's say... Color Care shampoo, and a large bottle of... Triple Nourishment conditioner. In my shower, for example, I have a small bottle of Herbal Essence [Drama Clean] shampoo, and a large bottle of Herbal Essence [Long Term Relationship for long hair]. I really love Herbal Essence-- right now it's my favorite brand. You don't have to get two bottles of the same thing, I try to get two different types. Here's some tips:

For Damaged Hair:

Buy a anti-breakage conditioning shampoo, and for conditioner get a nourishing conditioner.

For Colored Hair:

Buy a color-care shampoo, and a nourishing conditioner.

For Flat, boring hair:

Buy a root lifting shampoo, and a volumizing conditioner. 

For Frizzy hair:

Buy frizz-ease shampoo and conditioner. Great if you can get it with Keratin, too. 

For Long Hair:

Nurishing shampoo, Anti-breakage conditioner. 

Hope this helps, leave comments if you have unanswered questions! 

-FerretGurl