Originally Posted by: PoleraIn between the terble staff and time signature there will be sharps or flats on the lines of the music bar. They tell you which key your in. For instance, a sharp on the top line indicates that the passage is in the G major scale until otherwise noted.

I hope i have helped...im not very adapt in musical thoery :(

Many, many years ago when I took piano in sixth grade, my teacher taught me a very good way to read the key signature on the staff. If the signs are sharps, then the key is one note higher than the last sharp, i.e., only one sharp (F#) means the key is G. If the signs are flats, then count down three from the last flat, i.e, last flat is Bb, then the key is F.