How do you style hair that seems to fall out whenever manipulated?
Before I style hair that seems to be falling out, I would first try and find out why the hair is so fragile. I would recommend seeing a doctor to check hormone levels, thyroid and pituitary excretions and a cancer screening. Medications can also cause hair loss or breakage. I would choose a style that requires very little combing and tension. A loose roller set may be the best. This would give the client body and curls that would last all week. She would use a satin hair bonnet at night to keep her hair from rubbing against her pillowcase to help reduce breakage and maintain her style. In the morning she can finger comb or use a very widely spaced comb to style her hair.
How can I make my hair straighter, longer and thicker?
Hair can be straightened by using a chemical relaxer, pressing with a straightening comb and flat ironing. The best way to lengthen hair is by keeping it well-conditioned, regular trims and by using the minimum amount of heat. If you have never had thick hair, you cannot make it thicker. We are born with the amount of hair follicles we will have for our lifetime.
I've heard that African-American hair can actually be some of the most fragile textures. Is this true? Why or why not?
There is condition called Fragile Hair Syndrome, which causes the hair to break continually, it can affect anyone. For African Americans it is more common for the hair to be fragile due to the curl pattern and lack of moisture in the hair shaft.
Sometimes a treatment that makes the hair smooth at the time (lots of heat, 
flat irons) ultimately damages the hair. What do you suggest doing while
styling to minimize damaging effects?
Flat or curling irons and excessively hot blow dryers can certainly damage the hair. While the styling effects look good at the time, one must be careful that the heat is not burning the hair or boiling the water inside the hair cuticle. Many flat irons reach heat temperatures of up to 400°F, this can be very damaging. The use of a thermal protector prior to using these heated appliances can help to protect the hair before the damage occurs.