I don't know if everyone teaches this but my professor recommended that we keep a tally of electrons when drawing the Lewis structure. For SCl2, I know S is the central and the two Chlorine atoms are peripheral atoms. I know S has 6 electrons and the Chlorines combined are 14 which is 20 electrons in total. Place a couple of single bonds in the structure and subtract 4 electrons from 20 = 16. Add 6 electrons to each Chlorine atom to satisfy the octet rule. Combined that is 12. So subtract 12 from 16 = 4 remaining electrons. These electrons will serve as lone pair electrons for S so place 4 dots around S.
I hope that helps.
MJF