Find middle "C" on the piano's keyboard. Middle C is the 24th white key from the left of the keyboard. If you can't locate it, turn on your guitar tuner and switch it to the "Sound" feature. Scroll until it is buzzing a C note. Match the sound of the tuner with the sound of the note on the piano.
Get familiar with the sound of the piano. Once you locate Middle C, hit the next 6 white keys in succession. These are D, E, F, G A and C notes. You may recognize these notes. From Middle C to the C note an octave higher, these notes represent the classic "Do-Re-Mi-Fa-So-La-Ti-Do" exercise. Play these notes several times so you become familiar with how they sound. Learning how to properly sing these notes will help you sing along with piano music. Note: Stay in middle C for now. Attempting to sing at higher or lower octaves in the beginning may cause you to experience pitch problems.
Begin the"Do-Re-Mi-Fa-So-La-Ti-Do" exercise. Play the notes on the piano first. Then repeat them with your voice. Sing slowly at first, and be sure to enunciate properly. To effectively project each note, a simple inhale-exhale exercise is recommended. This is simply done by inhaling before each note. The notes should be sung as you exhale.
Turn on your guitar tuner to help with any problems staying in tune. The tuner will indicate whether or not you are on key. Pay close attention to the gauge on the tuner. Repeat this exercise for 30 minutes per day for 1 month. Do not increase your tempo until you are able to sing the notes properly.
Sing along with the piano. If you don't play piano, recruit someone who does. You can have him play and hum some simple melodies. Tunes you are familiar with are recommended at first. Sing along with the melodies. If you are off key, you will notice a difference between how your voice and the notes coming from the piano.