Step 1: Find valence e- in all atoms. Add them together.
S:2x6=12
F:2x7=14
Total=26

Step2: Find octet e- for each atom and add them together.
S:2x8=16
F:2x8=16
Total=32


Step3: Gives you bonding e-. Subtract step 1 total from step 2
32-26=8e-

Step 4: Find number of bonds by diving the number in step 3 by 2(because each bond is made of 2 e-)
8e-/2= 4 bond pairs
Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.
26-8= 18e-=9 lone pair
Use information from step 4 and 5 to draw the lewis structure.
Put atom with lowest electro negativity in the center. Arrange the remaining atoms around it. Finally put the bond pairs and lone pairs of electrons on the atoms.