10 steps how to sing well

1. Find a vocal coach or qualified voice teacher if you can afford one. It could be someone you know who has gone through voice training already, but it is always good to look for a professional. Incorrectly performed techniques can ruin your singing voice. Investing in an experienced vocal coach is well worth the money. If your voice is weak, know that this is usually caused by under-developed muscles or improper use of the resonators (the pharynx, the hard palate, and the nasal cavity).
If you cannot afford or do not want the dedication that comes with hiring a professional voice coach, consider joining a local choir. There are also a few learn at home vocal training courses out there such as Singing Success, Sing and See, Singorama, Singing for the Stars and Vocal Release, but be sure to do your research to see which ones have really worked for other singers.
Be careful in your choice of teacher -- there are some bad ones out there. If you're in a school with choir, get in there and sing your heart out! If you don't want to have to pay for voice lessons try to google some singing and vocal exercises.

2Learn your vocal range. This is essential, as singing pieces written for the wrong range may strain your voice. To get into your higher range work on developing the "mix voice" or "passaggio. The mix voice is a blend between the lower range "chest voice" and the upper range "head voice". There are various videos on youtube explaining how to develop your mix and one good exercise is the 'vocal fry" The tone of your voice is much more important than range. People will love or hate your voice based on its sound character, not how many notes you can hit. Never sacrifice tone for range (stay inside your range). Your range can change over time and with maturity and training but vocal chords can not learn to physically change.

3Correct your posture. Stand tall with one foot slightly in front of the other one, feet shoulder width apart. This allows you to breathe easily and to allow maximum lung capacity to allow better notes and phrases. Stand up straight, shoulders back and down, floating over your torso. Make sure that your chest is high to give room for your lungs to expand and contract. Relax your jaw, relax your face.

4Breathe properly. The voice is best described as a wind instrument, because breathing is 80% of singing and proper singing begins and ends with proper breathing.

5Get to know your singing tools so that you are more familiar with how everything is supposed to move and feel.
Touch the top of your collar bone. About a half of an inch below your finger is the top of your lungs.
Find your nipple line. This is the place where your lungs expand the largest.
Find your ribs. Your ribs move like bucket handles attached to your spine and your sternum. When you breath in, they move upward and make your chest expand, when you breathe out, they move downward and your chest decreases.
Find the place right below your sternum where your rib cages meet. This is the bottom of your lungs and the housing of your diaphragm. The reason your stomach may pooch out when you breathe deeply is because your diaphragm is pushing down on everything below your rib cage, not because your lungs are in your stomach.

6Develop and show your confidence. Do not care what people think, just keep practicing and you will gain confidence. Make sure that you are ready to sing.

7Always warm up before you begin singing or doing practice exercises. You should always warm your voice up in this pattern: middle range, low range, then high range, then back to middle. You should spend at least 10 minutes on each range and do not stress your voice if you're frustrated and cannot hit a note. Warm back down or up to your comfortable range and then try again, carefully. Other things to practice:

Dynamics - Sing a comfortable pitch and start very softly, crescendo to loud then decrescendo back to soft. Do this with many different vowels and pitches. Dynamics are variations the intensity of your resonance. Even the simplest use of dynamics will make your songs come alive, and the more you practice, the louder and softer you'll be able to sing healthily. When reading music, from quietest to loudest, dynamics marks are as follows: pp (pianissimo, very quiet), p (piano, quiet), mp (mezzo piano, medium quiet), mf (mezzo forte, medium loud), f (forte, loud), ff (fortissimo, very loud). When you start out you will probably only be able to sing from mp to mf, but your range will increase with practice.
Agility - Try singing from do to sol to do really fast back and forth, trying to hit all of the notes. Do this in increments of half steps on different syllables. This will help your voice become more flexible.

8Pronounce your vowels correctly. Words are truly nothing but a constant succession of vowels with consonants dropped in occasionally to create meaning. So practice all your vowels at every pitch (high, low and in between). In English there are very few pure vowels. Normally, we will encounter diphthongs which are two or more vowel sounds elided together. In classical singing, the singer will sustain the note on the first vowel and then say the second on the way to the final consonant. In country, singers like to slide through the first vowel and elongate the second vowel on the sustained note. Where as: a classical signer would sing "Am[aaaaaaai]zing Gr[aaaaaai]ce" and a country singer would sing "Am[aiiiiiii]zing Gr[aiiiiii]ce". If you can, always sing the first vowel for as long as you can before letting the second vowel in. Here are some pure vowels to practice with: AH as in "father", EE as in "eat", IH as in "pin", EH as in "pet", OO as in "food", UH as in "under", EU as in "could", OH as in "home". Try singing all above of these vowels while maintaining your core sound which is the resonance in the mask of the face. You can do this in many ways. Some examples of singing exercises that use vowels are just singing "mee may maw mow moo" and fluctuating the voice as you go. This warms your voice up and gives you practice with singing vowels.

9Practice scales. You need to do this often if you have pitch problems. Most coaches will recommend 20-30 minutes a day when starting out. Practicing scales will also strengthen the muscles used for singing and give you better control. To practice scales, identify your range (tenor, baritone, alto, soprano, etc.) and know how to find the notes that cover your range on a keyboard or piano. Then practice the major scale in every key moving up and down using the vowel sounds. At some point you can start working in minor scales as well. Solfege (Do,Re,Mi,...) is also an effective tool for improving pitch problems.

10Be reasonable with your self-expectations. Regardless of where you are coming from, if you can devote 20 minutes or more a day to practicing scales and songs you can expect measurable improvement within four weeks. Most pitch problems can be corrected within 3-4 months. Understand that your progress is linked to your ability to practice daily (as with most training). If you only do 15 minutes a day, a few days a week, you could spend a year or more. If you devote yourself you could transform your voice in three months. Everyone is different.