In either style, the main elements are the same. Each must consist of three main branches, stems or flowers. These symbolize "shin" which means heaven, "soe" or mankind and "hikae" which means earth.The tall branch, or the shin, should be one-and-a-half or two times the length of the container. The second branch, or soe, should be three-fourths the length of the shin, and the hikae is three-fourths the length of the soe. In the end, these three elements form a triangle. Using those parameters, use the plant material as a source for inspiration.
Next consider the passage of time--this is symbolic of ikebana. Branches and flowers are carefully selected to last, change and represent nature. It's a living art form. Flowers never stay the same, so the arrangement created today will not be the same tomorrow.