Cremation's been done for centuries, it's only in recent centuries that people have been buried. It's extremely recent that people have been buried in concrete and metal vaults instead of wrapped in a shroud and buried like that, or wrapped in a shroud and placed in a simple wooden coffin placed in the ground.
If it was even remotely legal, placed on a burial pyre and cremated that way. YAY for ancient burial ceremonies!
Barring that, cremated, and my ashes thrown to the wind, thrown in the fire, scattered across the water (as in a lake, river, or ocean), and scattered across the earth. In other words, I wish to be returned to the 4 elementals that created me.
And definitely, DONATE MY ORGANS FIRST. I carry an organ donorship emblem on my state ID, so that's a definite will most likely happen. However, do not use my body for science...no, thank you very much, I do appreciate science, but I do not wish my body to be used as a science project.