Immediately after contact, washing with soap and cold water (to avoid opening the pores) may reduce the risk of a reaction. However, the best way to prevent a reaction is to not come into contact with the plants in the first place! Therefore, it's very important to know where they are found and what they look like.
Generally, poison ivy is east of the Rockies, poison oak is in the West, and poison sumac is also east of the Rocky Mountains, in very wet areas. Poison ivy does well in disturbed areas and as such is extremely common in suburban and exurban areas.
Poison oak and poison ivy have leaves in groups of three with the middle leaf extending out longer than the others. They also have a reddish tinge to them, from the urushiol making its way to the surface and reacting to oxygen. The stems and vines have an even more concentrated amount of urushiol, so coming into contact with the plants in the winter will likely be worse and harder to avoid (because they can't be recognized by their leaves). Burning them will release the chemicals into the air, which may still cause reactions.
Urushiol is extremely stable, so unless it is washed off clothes (regular laundering with detergent should be fine) or tools (soap and water), it could still easily cause a rash a few years later.