There are many approaches to singing. Depending on which style of singing you are doing the basic principles to learn to sing well remain the same. As with all musicians you have to spend time practicing and learning your instrument. In this case your instrument is inside your body. As a result it is more temperamental than any instrument you would otherwise have control over.
In this case when learning your instrument, you have to know the factors that will influence your voice.
There are a few basics that apply to singing that is universal.
1. Make sure that the material that you are using is suited to your voice type. If a song is not right for your tessitura then you put strain on your voice and may damage it.
2. It is important to warm up your voice before you start singing and then also after you finish singing to warm down the voice.
3. It is important to do vocal exercises every day. The vocal chords are muscles and will improve with exercise and will grow stronger.
4. Do breathing exercises. Make sure that when you breathe, there is no lifting of the shoulders. If the shoulders are lifted there is a tensing of muscles and will constrain your breathing.
5. When breathing in, expand your rib cage to enable you to take in more air.
6. To ensure that you are breathing correctly, practice breathing in with both hands positioned on your lower back just above the hips. If you breathe in and there is an expansion of the lower back muscles as well as the lower abdominal muscle, your support will then be in the correct position. Another method of making sure that your support is in the correct place without using your hands is to make use of a belt so that you can get use the feeling of breathing that low down in your body.
When all of these points are applied and practiced diligently everyday you can learn how to sing well. It is however always better to work with a vocal coach or teacher. The reason for this is that as a singer you cannot always hear the things that you are doing wrong, and you can therefore learn wrong techniques that might damage your voice. It also helps to record your lessons and exercises so that you can hear what it sounds like. When you sing the sounds that your voice is producing is different to what you can hear on a recording. This will then help you to hear the mistakes that you are making and put those together with the physical sensation of singing.