The treble clef and ledger lines
Read and write notes above and below the staff in the treble clef.
Above and below the staff
Five lines are enough for the notes from E4 to F5. For higher and lower notes, short ledger lines are written above or below the staff: each is a piece of the staff extended, only not drawn in full.
Count just as inside the staff: line, space, line. Above the fifth line sits G5; on the first ledger line above, A5; above it, B5; on the second ledger line, C6. Below the staff: D4 under the first line, C4 on the first ledger line, B3 under it and A3 on the second ledger line.
Up from the top line: F5, G5, A5, B5, C6
Down from the bottom line: D4, C4, B3, A3
Don't guess a note on a ledger line by its look. Find the nearest note you know on the staff and count the steps: every line and every space is the next note.
Practice: Read the notes
Practice: Write the notes
Landmark notes
The quickest way to read is from a few landmark notes: C4 on the first ledger line below, G4 on the second line (the treble clef marks it), C5 in the third space, G5 just above the staff and C6 on the second ledger line above. No note is more than four steps from a landmark.
The landmark notes of the treble clef
The same landmarks on the keyboard: C and G, five and four white keys apart