The most important info that all prospective or even professional singers should know .....


Breathing is the thing that can either prolong, or interrupt your voice, so breathe wisely 

Proper breathing is very important for singers. Practise breathing exercises regularly and you will notice a great change in your singing.

To breathe is your prerogative. Air is available for free. So go ahead and take a deep breath of air when you sing.Do not breathe with your shoulders going upwards. When you breathe your tummy should be pushed outwards. Your tummy should get enlarged like a balloon. When air is pumped in a balloon, the balloon gets enlarged. Similarly when you inhale, the air inside your lungs should enlarge your tummy
Sing From Your Diaphragm

The correct way is to sing from your diaphragm. Singing from the throat is the incorrect way to sing. This will eventually damage your vocal cords.

Practice! Practice!! Practice!!
Practise is very important. Even the very talented have to practise. Follow the old adage - 'Practise makes perfect'. Set aside a time for practise. At least half an hour a day is good to keep your vocal cords in shape. Divide your practise session. Sing for 15 minutes in the morning, 15 minutes in the evening. This way you will not feel like practise is a chore. You'll be amazed at how wonderfully you sing after regular practise. We humans are known to be great procrastinators. Do not procrastinate. Just do it.
Physical Exercise
  Aerobic excercises are very important because they increase your stamina so that in case when you had to hold or sustain your  breathing for a long time during singing it will be very useful, if you can't do it for any health reasons then any kind of physical exercise is good that can be tolerated by you .           Even just walking is good for your health.
Where and when to sing?
                                                                                                  Try to Sing whenever and where ever you feel comfortable,  also practice in front of the mirror. Sing to your family members, your friends and sing whenever/wherever you get an opportunity to sing. 
Warm Ups
  Before a performance you should warm up your vocal cords. Warm up with light vocal exercises, lip drills, tongue rolls and scales. If you sing without warming up you could hurt your vocal cords. Just like an athelete warms up before a marathon, singers need to warm up their vocal cords before a performance-athon.
Jumping jacks!!!
Physical exercise has proven to be beneficial to combat nervousness.
If you feel nervous before a performance try jumping jacks.
Don't worry if you can't reach the high notes. Instead try to sing with emotions. Trying to sing high and cracking on the high notes would impair an overall brilliant performance. Instead try singing with feelings and stay within the range (border) of your voice to captivate your listeners.
High Notes
Open your mouth widely as if you are eating an apple.
Hydration very crucial!
Keep your vocal cords hydrated at all times. Drink plenty of water. A dry throat is like a machine without lubricating oil, which makes singing very difficult. Hydration is very important for your voice.
Avoid dairy products just before!!!
At least 3 hours before any performance. Dairy products like milk, chocolates, cheese, custard, yoghurt etc... create sticky mucus in the throat.
Avoid or minimize cold stuff....
Ice cream and cold drinks as much as possible, Ice tightens the vocal cords your vocal cords must be worm and well hydrated to sing well.
Do not smoke XXX
As smoke sticks to the vocal cords and burns  the vocal cords  and further impairs your breathing capacity as well as your endurance  by damaging the lung tissue. Chronic smokers develop thick voice and loose melody. Chronic smoking women loose their natural voice and develop masculine voice.
As you all very well aware smoking eventually leads to throat cancer,lung cancer and many more. So if you wanna live long and sing along stay away from smoking. 
Do not drink alcohol XXX
 It dehydrates you and causes dryness to the vocal cords, not only that it can directly damage your throat mucosa (thin top layer which helps with lubrication and protection  from bacteria and virus etc.).  Some times it leads to aspiration that means your food might enter your lungs which could be life threatening.
Alcohol stimulates more acid in your stomach  and can lead ulcers and acid regurgitation/Acid Reflux (GERD) and causes sore throat.
Sore Throat remedy
The best remedy for a sore throat is salt water gurgle. Add little bit of salt to a glass of luke warm water and gurgle. Gurgle at least 3 times a day. 
Microphone Techniques
The best position to hold a microphone is to hold it at least 2 to 3 inches away form the mouth. Do not eat the microphone . Eating the microphone is a term used when you place the microphone too close to your mouth. If you place the microphone too close to your mouth this will produce bad noises. The consonant's Bah and Pa particulay will create pops (bad popping noises). A technoligical term for this is called sibilance. Move back from the microphone when you have to sing high notes. There are different kinds of microphones like unidirectional, omnidirectional, dynamic, condenser and many other types so be mindful about which mic you are dealing with.
How to get a record breaking deal?!!!
To get a record deal you should first make a demo consisting of 2 to 3 songs. Your demo should not be more than 3 minutes long. Send your demo along with your recent photograph and a short biography of yourself to record companies or Indian Idol if you think you are really good!!!. Participate in all the singing competitions to get recognition as well as experience.