Hair Stats: These are averages.
The average scalp has between 100.000 and 120,000 strands of hair.
The average scalp loses between 50 to 100 hairs per day. The average rate of growth for scalp hair is 1 mm every 3 days, or about 1/2 in per month.
The average life span of a strand of hair is between 2 and 6 years. Obviously very long haired people have hair with longer life spans. This is genetically predetermined.
About Your Hair: Hair has three basic layers. The inner most core is the medulla. Secondly is the cortex. The medulla and cortex are the heart of the hair. It is where the color and resilience of the hair lies. The outer layer is the cuticle. The cuticle is the protective coating. The primary component of hair is keratin. It also contains dead amino acids, primarily cystine. Keratin is a fibrous, sulfur-containing protein. The protein is insoluble in most solvents. That means that hair is very chemically durable. That is why it takes such powerful base chemicals to permanently change it. Despite its durability it is damaged with repeated onslaughts of styling abuse. Once the outer layer of the hair, the cuticle, is severely damaged, there is very limited help available. Hydrolyzed human hair Keratin protein generally found in the form of placenta, is the best penetrating, reconstructing substance available. Short of that, the damaged length must be cut off to improve the looks and manageability of your hair.

1. Minimize damage: Braids are great for minimizing the need for excessive brushing, styling treatments and chemicals. Perms and permanent colorings damage your hair. No way around it. Dark hair dyes can be especially toxic too.
2. Minimize extreme heat: Sun exposure, curling irons, and blow dryers damage your hair. Protect it from harsh sun exposure with a hat. Let it dry naturally or with low heat. Many conditioning treatments are heat activated but only low heat is needed.
3. Nutrition and stress: They play and important role in our hair growth and health. We all go through phases where we loose more or less hair. If you have ever lost your hair due to stress you know what I mean. It happened to me. It is scary, and so often we only see it in retrospect. Be good to yourself. Exercise regularly and you will feel and look better. No fad diets! Drink plenty of water. Most people don't drink enough. Your hair is a window to your physical health. If your hair is dull and breaking off, examine your life along with your hair styling regimes. Some medications can also cause hair loss. Supplements are very controversial, use your own judgment.
4. Stop smoking. Do I even need to say it. Smoking constricts your circulation and decreases the blood flow that supplies the nutrients and oxygen your hair (and skin) needs.. 
5. Be Gentle and loving with your hair. It is easy to get in a hurry and get rough with your hair. Don't do it. Just let it be tangled until you have time to comb it carefully, especially when it is wet. Hair is weakest when it is wet. If you have to go out, put a hat or scarf over it. Having tangles in you hair doesn't damage it, rough detangling does.

Don't Go Shopping for Hair Care Products Without Me by Paula Begoun: An excellent book. Full of great hair care product information.
A Lifetime of Beauty by Sharon Faelten and the Editors of Prevention Magazine: A very good book with a wide range of health and beauty tips.
The Cure for All Cancers by Dr. Hilda Clark: This woman has received a lot of alternative publicity and FDA harassment over this one. She hit them at the pocket book level. I believe the health care suggestions to be sound advise although not always easy to live by.