The most basic scale is the chromatic scale. It is made of twelve notes that are a half step apart. The chromatic scale, beginning with E, is: E, F, F#, G, G#, A, A#, B, C, C#, D, D#. You can easily play a chromatic scale on the guitar by starting with an open string and playing every fret until you reach the octave at the twelfth fret. The diagram of the linear form of the chromatic scale shows it being played on the sixth string of the guitar (the E string).
The box form of the chromatic scale involves playing a five-fret stretch on every string except the 3rd string (G string). This is easily accomplished as you ascend the scale by using your fourth finger on the fourth and fifth frets in the box form. However, when descending, you may find it easier to play with your fingers in the order 4, 3, 2, 1 and 1 again. This would put your first finger playing the second fret and the first fret in the box form.