Premature greying and falling of hair?  

Well one main cause for hair falling out is stress. You just need to relax more and if it persists. then see a barber, they would know more.

Heredity
Stress
Age
Pollution
Food
Diseases

So many things cause premature greying and hair fall.

You should try to eat more fresh vegetables and drink more fluids. Be healthy and practice meditation for stress release. :)

Sometimes a heriditary factor runs in the family members, which remains unresponsive to any kind of treatment.

Herbal Medicines
First and foremost, the scalp of the affected person should be energetically massaged daily for 10 to 15 minutes with fingers, after cleaning it with water. This mechanical action activates the hair follicles by ensuring blood circulation, and warms up the scalp.
Amla Hair Oil: Amla hair oil can be made at home itself, by adding fresh juice of Indian gooseberries to pure coconut oil. This should be boiled till the Amla juice is completely absorbed in the oil. This oil should be applied after the above said massage.
The powder of amla and Bhringaraj is also used internally in a dose of one teaspoonful thrice daily with milk or water.
The pulp of amla and mango mixed together is used externally on the scalp.

Ayurvedic Remedies
Some medicated hair oil available over the counter for hair fall are:
Neeli Bhringamalaka Tailam
Bhringaraj Tailam
Brahmi Amla Kesha Tailam

Anyone of these oils should be applied onto the scalp, twice a week at bedtime. Regular washing of the hair with shikakai is a must and soap should be avoided. Greying of hair and hair fall stops in many cases, after 2 to 3 months usage of these oils.
Combination of Bhringaraj churna ½ teaspoonful thrice daily and Bhringaraj capsule, one capsule twice daily with water after meals along with Bhringaraj Tailam locally yields very good results.
Shad Bindu Tailam is used for inhalation (Nasya) once daily for 1 to 2 months.
Neem oil is also used for inhalation twice daily for about a month. Along with this only milk is taken in the diet.
Triphala Churna taken 5 to 10gm at bedtime with milk or water for a long time can prove very effective in curing greying and falling of hair.
Hair sure oil (Platinum Remedies) is also very good.
Sesa oil (Ban) proves very useful if used for 3 months.

Many people say that they graying of hair is a sign of wisdom. There is truth to this because men, as they grow older have gained experiences and therefore, will be more wise compared to those boys whose hair is till fresh and young. Some of the responders have already discussed how the hair turns to gray. But I am more interested in how we could use our experiences to be wise...

Stress and thinking too much leads too graying of hair, hairloss and even dandruff so better take it easy. Chill!