Anything with opposite leaves growing in couples (see all maples) is not poison ivy.

If all the leaves are simple is not poison ivy. They need to be composed by several leaflets

Anything with five or more leaflets in the leaves is not poison ivy but could be poison oak or other poisonous relative. Some other Toxicodendron have 5, 7 or more leaflets.

Check for how "soft" and flat is the surface and how the light is absorbed