See your String-O exercise booklet for the specific exercise that your teacher has assigned for you when any of the following String-O calls are posted.  See below for some options you can do in addition to your assigned exercise (with your teacher's permission).

1/2 Bows

Pg. 16, #'s 73-76 from Janice Tucker Rhoda's Complete Technique for Violin, Book 1

1/4 Bows

Pg. 16, #'s 69-72 from Janice Tucker Rhoda's Complete Technique for Violin, Book 1

1/8 Bows

Pg. 15 or pg. 25, #'s 115 or 117 from Janice Tucker Rhoda's Complete Technique for Violin, Book 1