In order to be able to read music it is essential to quickly recognize the note on each space and line in the staff. This is achieved with a lot of practice and patience.
However at first it can be helpful to memorize the order of the notes in the spaces and lines. For example in the G clef, the notes on the lines are E, G, B, D and F. In the spaces the notes are F, A, C, and E:
The space notes are easy to remember since they make the word FACE. For the line notes you can use the following phrase: Every Good Boy Does Fine.
The F clef:
See Reading Music in the Tutorials section.