I think the best material is used panty hose. believe it or not. Cut strips and tie down. It is gentle and stretchy and strong, it won't injure the stem and it expands as the stem expands and doesn't cut into it.
That said I use the black metal spring "binder" clips with the two fold down handles on the side of the pot, then hook a bent paper clip on the branch and to the clip.
That said I use the black metal spring "binder" clips with the two fold down handles on the side of the pot, then hook a bent paper clip on the branch and to the clip.