First you position the headboard of your bed an inch from the wall. Second, set your girl up doggystyle and make sure her head is only a few inches from the headboard. Third, as you're pounding away, her head will hit the headboard which will, in turn, hit the wall making a galloping noise. Finally, as all this is happening, wave your arms in the air and make noises like a camel.
"My girlfriend got a concussion last night when we tried out the flying camel"