G major has 1 sharp (F#) which falls on the seventh note of the scale, Remember all major scales have the same arrangement of tone and semitones - i.e. T-T-S-T-T-T-S In the key of G major the seventh is raised to form this pattern.
 
Important:
In the examples pictured there is a 'key signature' just after the clef. F# is indicated on the top line, this means that all F's in this music are to be automatically sharpened (raised a semi-tone) You can also be asked in exams to write out the scale without key signature which means placing a sharp (or flat) just before the note.


Listen to G major (roll mouse over image)