Learn the letters of the musical alphabet, A,B,C,D,E,F, & G.
Memorize the names of the lines and spaces for the "Treble Clef" and the "Bass Clef." The names of the lines for the treble clef are E,G,B,D & F. The names for the treble clef spaces are F,A,C, & E. An easy way to remember the treble clef lines is to use the letters as an acronym for "Every Good Boy Does Fine." The treble clef spaces are easy to remember because the letters spell "Face."
The names of the lines for the bass clef are G, B, D, F, & A. The names for the bass clef spaces are A, C, E, & G. You can use the sentence, "Good Boys Do Fine Always" to remember the bass clef lines. Use the sentence "All Cows Eat Grass" to remember the spaces for the bass clef.
Become familiar with hearing and singing the pitch for all of the musical notes by listening to musical scales. The reasoning for this is that if you know what a note sounds like, you can sing the right pitch when you see the note on a sheet of music.
Learn the note value for all of the different notes you will commonly see as a beginning musician. This includes the "Whole Note," "Half Note," "Quarter Note," "Eighth Note," and "Sixteenth Note." The whole note is equal to two half notes. The half note is equal to two quarter notes. The quarter note is equal to two eighth notes, and the eighth note is equal to two sixteenth notes. There are more advanced note values. However, as a beginner you can focus on the basic note values.
Study the different "Time Signatures" to ensure that you know how to assign the proper note value to each note that is on the musical staff. When reading a time signature, the top number indicates how many beats are in each measure. The bottom number indicates which note gets 1 full beat. For example in a 3/8 time signature, there are 3 beats per measure and the eighth note gets 1 beat. In a 4/4 time signature, there are 4 beats per measure and the quarter note gets 1 beat.
Practice keeping the beat by tapping your foot. Each time your foot hits the ground is one beat. When your foot goes up and down four times, that is the length of a whole note. When your foot goes up and down twice, that is the length of a half note. Up and down one time is the equivalent of a quarter note. Each time your foot goes down and up it is the equivalent of two eighth notes.
Become familiar with the volume markings on a piece of sheet music. For example, if you see a "P" it means play or sing the music softly. If you see an "F" it means play the music loud. The more Ps you see the softer you play/sing. The more Fs you see, the louder you play/sing.