Trick-or-treaters can head to the Gainesville square at 3 today to scare up candy from the downtown merchants. The event will be 3-5 p.m., and many shops will set up outside to pass out goodies. A costume contest also will be held at 4:30 p.m. For all trick-or-treaters and anyone planning to be on the roads this evening, stay safe with these tips from local authorities.