Look for a note without a stem. Most musical notes have stems extending from the top or bottom of them (depending on whether they are over or under the middle line of the staff), but whole notes do not. Find a note without a stem and you have located a whole note. Check the time signature, which can be found on the far left hand side of the musical staff. In 4/4 time (otherwise referred to as "common" time), a whole note represents four beats, or an entire bar. The whole note has a hollowed-out center.
Find a note with a hollowed out center and a stem, which marks a half note. Each note has a value dependant on the amount of time it takes up out of one individual bar. A half note, therefore, takes up half of a bar. Play this note and let it ring out for half a bar when you encounter it in guitar sheet music. There can be two half notes in a bar.
Locate a note with a filled in center and a stem. If you asked someone to draw you a musical note, they would probably draw a note with the same value as this. Notes with a filled in dot and a stem are quarter notes, meaning they take up a quarter of a bar. There can be four quarter notes in a bar.
Look for a quarter note with a small tail dangling from the top of the stem. This tail is an indicator that the note has half the value of a quarter note, making it an eighth note. Two eighth notes together can be joined at the top of the stem by a straight line. Think of this as their tails meeting in the center; notes joined together by one straight line are eighth notes. There can be up to eight eighth notes in a bar.
Find an eighth note with an extra tail. The extra tail means this note is a 16th note. You may encounter 16th notes in guitar solos or other fast-paced sections of the music. Two 16th notes can be joined together in the same way as eighth notes, but there are two lines connecting them, as opposed to one.
Locate a note with a dot after it. This is the most complicated note value to work out. Halve the value of the note preceding the dot, and then add that onto the value of the original note. For example, imagine a whole note with a dot after it. A whole note represents four beats in a 4/4 bar. The dot adds half onto the original note's value. Half of a whole note is two, and added onto the whole note's original four, that makes six beats. Add half to a note's value if it has a dot next to it.