All articles ever written on Lomography.
If you make doubles with yourself, you can shoot a whole layer on a certain subject. Then rewind the film, insert it in (the same or another) camera and shoot a second layer. I like the repetition of subjects, form, structures. Good subjects to use are plants and flowers, I shoot one film with fruit and vegetables (be careful in supermarkets, sometimes they are unfriendleye there!) or one layer with my beloved dog.