First, you need to have a periodic table that contains the electronegativities values. once you have them, you just need to subtract the values of the atoms and each bond. I have attached a table with these values. also, it does not matter then order in which you subtract them because they are always positive values. even though you get negative values in your calculator, just make it positive.
H-S----> 2.1 - 2.5= 0.4
H-Cl---> 2.1 -3.0=0.9
H-O---> 2.1- 3.5= 1.4
H-F----> 2.1 - 4.0= 1.9
HF is the most polar because it has the highest electronegativity difference.
H-S----> 2.1 - 2.5= 0.4
H-Cl---> 2.1 -3.0=0.9
H-O---> 2.1- 3.5= 1.4
H-F----> 2.1 - 4.0= 1.9
HF is the most polar because it has the highest electronegativity difference.