Organic matter must have hard parts, such as shells, bones, teeth or woody tissues. However, even very fragile organisms, such as insects or jellyfish, can become fossils under very favorable conditions.

Creatures must be prevented from being destroyed immediately after death. If a creature's body is partially crushed, decayed or severely weathered, it may change or cancel the possibility of this creature becoming a fossil.

Organisms must be quickly buried by a substance that can hinder decomposition, and the type of this buried substance usually depends on the living environment of the organism.