Hey,
Different colleges have different admission procedure for B.Com. Colleges like that of the Delhi University take admission based on the marks scored in 12th boards. All the good colleges affiliated to Delhi University usually have cutoffs as high as 96 percent or above. On the other hand,there are colleges like Jamia Milia Islamia or Banaras Hindu University,Varanasi that conduct entrance examination and the selection is based on your performance in that test.
Hope this helps.
Good luck.