It is important to be able to sing any desired pitch accurately. A good way to develop your pitching ability (intonation) is to play,, or have someone else play notes on an instrument (e.g., keyboard) and copy the pitches with your voice. Some people find this easy immediately while others have to work at it for a while before they can do it.
Listen carefully to the pitch being played and trust your body to be able to produce that pitch. Relax and let the sound come out naturally. The following examples demonstrate this exercise. Listen to the recording to hear first the keyboard and then the voice produce each pitch. Each example is then repeated with the keyboard playing the pitch, followed by a space left for you to reproduce the pitch with your voice. Each pitch is a half note (two beats) and is followed by a half note rest. Sing the pitches with the syllable la.