How to tell a wasp from a yellowjacket

Paper wasp appearance: 

Paper wasps have slender, segmented bodies with a thin waist. Paper wasps also have orange-tipped antennae.

Yellowjacket appearance:

Yellowjackets have shorter and thicker bodies than paper wasps. Yellowjackets have black antennae.

Paper wasps in flight:

Paper wasps dangle their long legs when they fly.

Yellowjackets in flight: 

Yellowjackets tuck their legs under their bodies when they fly.

Paper wasp nests:

Paper wasp nests resemble an open honeycomb or upside-down umbrella. They often build their nests on man-made structures such as eaves or lawn furniture.

Yellowjacket nests:

Yellowjacket nests have a single opening that is often hard to see because the nest is underground. Some species of yellowjackets will construct nests in wall voids or exposed under eaves of houses.

Paper wasp behavior:

Paper wasps feed on damaged fruits and can be found on flowers looking for nectar. They do some pollination, but are not efficent because they don't have fuzzy bodies on which pollen can stick. They scrape wood from structures to make their nests. 

Yellowjacket behavior:

Yellowjackets are picnic pests; they're drawn to protein sources, such as grilled meat. They also go after sweet liquids like soda and juice. Instead of visiting flowers for pollination, yellowjackets go after other insects.

Paper wasp aggression:

Paper wasps are generally docile and avoid humans; they usually will sting if the nest is disturbed. They can sting repeatedly.

Yellowjacket aggression:

Yellowjackets are more aggressive than paper wasps. They defend their nest, but will also sting unprovoked. They are prone to swarm attacks if their nest is threatened.