Put brown sugar, butter, corn syrup, salt and baking soda in a large microwaveable bowl. (All microwaves are slightly different and you may need to adjust your times appropriately) Microwave on HIGH and boil for 2 minutes (I do 1 minute, stir; 1 minute, stir; 30 seconds, remove). Spray non-stick cooking spray, such as PAM, in a large paper grocery sack. (I just use my tupperwave microwave bowl with lid that I cook the caramel in.) Put popped corn in bag (in bowl) and pour (stir) caramel mixture over it. Put in microwave on HIGH for 1 minute, shake; microwave 45 seconds, shake; microwave 30 seconds, shake; microwave 30 seconds, shake. Pour caramel corn onto a cookie sheet to cool. (I use a silicone liner in my cookie sheet, so there is no sticking) Stir while cooling so the pieces separate.