The Treble Clef spirals around the second line from the bottom. This spiral tells us that notes on this line are G.
From here we can figure out the other note names simply by going forward or backward through the musical alphabet: A,B,C,D,E,F,G.
If we need more notes above or below the staff we add Ledger Lines, which extend the range of the staff. (Middle C is the first ledger line below the staff in Treble Clef.)
The Bass Clef has two dots, above and below the second line from the top. The dots tell us that this line is F.The note names in Bass Clef are:
Middle C is the first ledger line above the staff in Bass Clef.
Learn about the Alto and Tenor Clefs