What are the ways of saying Basmalah (i.e., “Bismillaah il-Rahmaan il-Raheem”) between the middles of soorahs?

It is only essential to recite "Bismilla hir rahmaa-nir raheem" once at the beginning of a sura, however if one recites part of a sura then go to the beginning of another sura in the same rakaah, then he must recite "Bismillah hir rahmaa-nir raheem" again before beginning of the sura. This is essential as each sura begins with this phrase.