The form of Sijo is basically the following -

3     4
4     4

3     4
4     4

3     5
4     3

Where each number represents a phrase of syllables, with a line break in between (space over about five spaces). In three stanzas of two lines each, the first stanza is an introduction, the second stanza is a development of the first, and the last stanza is a conclusion. See some of the examples of Sijo inside.