Determine the age of the student. Piano methods are available to accommodate very young beginners, late elementary students and older beginners, including adults. Age-specific methods tailor learning to each individual. Books for young beginners have lots of colorful pictures to keep their attention. Adult methods cut out these cute little graphics and focus more on technical details.
Determine the goals of the student. Does the student want to learn to read music or to play by ear? Does the student have special needs that could make learning more difficult? Some books teach note reading, and some focus on ear training. Others teach only treble clef notes and use chords for left-hand accompaniment.
Consider the rote method of learning to play the piano. This method relies on the demonstration of playing simple melodies and having the student copy the teacher. John Thompson's "Teaching Little Fingers to Play" uses this method. Students learn to play a melody, and then the teacher shows them what the music looks like on paper.
Consider the Suzuki Method of learning. This method teaches students to play the piano by ear. Note reading comes later. The advantage of this method is that students can play more songs earlier than by note reading alone. The disadvantage is that some students rely too heavily on ear training, preventing them from reading the notes on the page.
Examine position-based playing methods. The Alfred series and Faber & Faber's "Piano Adventures" use this method. An advantage to position playing is that students can play more fluently and learn at a faster pace. Students with special needs may progress more quickly with this method because of its simplicity. The disadvantage to position-playing is that it sometimes inhibits note-reading. The students can have a hard time playing notes outside of the standard five-finger position.
Consider pre-programmed methods that use a set of lesson, theory, technique and performance books. The lessons are preset, taking any guesswork out of where to start and stop each lesson. The Alfred series and Faber & Faber series use this method, as does Bastien's "Piano Party" method books.
Browse through books on the chosen piano method. Music stores offer such books. Many books using each method are available from different publishers.