Reading notes
Ledger lines
Ledger lines are short lines added above or below the staff for notes that don't fit on its five lines. They continue the staff's pattern of line, space, line, so you read them by counting on from the nearest staff line: one ledger line below the treble staff is middle C, two is A.
Read it, then play it
Play the note you see on the staff. The exact key counts: how high the note sits tells you which octave.
Ledger-line notes in treble and bass clef
One and two ledger lines below and above each staff, with the space just past the first line in between:
How to count them
Treat each ledger line as one more staff line. From the bottom line of the treble staff (E) count down: D just below it, C on the first ledger line, B under that, A on the second. Going up from the top line (F): G just above it, A on the first ledger line, B, then C on the second.
The ones worth knowing by heart
Middle C on both staves, the A two lines below the treble staff, the C two lines above it (C6), and the E and C below the bass staff. With those fixed, everything else is one step away.
When there would be too many
Past three or four ledger lines, music changes clef or writes 8va: play everything under the dotted line an octave higher. 8vb means an octave lower.