Hmmm... In the tanning bed scene, it doesn't exactly show who dies first because both girls are screaming, then it quickly cuts to their funeral.
In Wendy's premonition, both Jason and Carrie are killed while seated in the front car. In the premonition, when the front car hits a hill, Carrie is ejected from her seat, followed by the first two rollercoaster cars (obviously one is containing Jason). Of course, the exact way the two die when rollarcoaster really does crash is unknown, but assumed to somewhat follow their original deaths.
Ashley Freund DIED; thrown from cart
Ashlyn Halperin DIED; thrown from cart
Frankie Cheeks DIED; thrown from cart
Lewis Romero DIED; smashed with a loose door
Ian McKinley DIED; falling
Erin Ulmer DIED; falling
Julie Christensen DIED; falling
Perry Malowinski DIED; falling
Kevin Fischer DIED; sliced by bent pole
Wendy Christensen DIED; falling
They die in the order they were sitting on the roller coaster, which is the order to how everyone dies. I hope this makes sense.