Identifying these plants can be tough, even if you're standing right in front of them. The old adage of "leaves of three, let it be" is a great saying to live by, until you realize a million different plants have 3 leaves.
Since identification can be tough, knowing what poisonous plants are common in the area you're exploring is super important. Here are some general rules for identifying these 3 plants:
Location: Western Poison Oak is common in California, Oregon and Washington, and Eastern Poison Oak is found in the South, Southwestern states of the US. Grows typically as a shrub or bush in open areas, and as a climbing vine when shaded or at the foot of trees.
Look for: Leaf structure that grow in sets of 3 with a wavy edge to them. Leaves are typically "glossy" looking (which is the oil on the surface of the leaf), and are typically green (which can turn yellow, red or brown depending on the time of year and health of the plant.
Location: All states except for California, Alaska, and Hawaii.
Look for: Always has clusters of 3-leaves, and the middle leaf is always bigger than the surrounding 2 leaves. These leaves can show different shades of green but tend to have a darker, waxier green on top.