Generally speaking........it falls to individual interpretation and literary analysis when determining what one believes to be symbolic, and what one believes to be literal.
The easiest determining factor for symbolism for me in the Old Testament is:
Does this same kind of story appear in other cultures as a means of explaining a current condition, either of humanity or the world?
Examples:
Creation
the Flood
the Tower of Babel
The wording in these stories (no matter which translation you use) mirrors the word choice of similar stories in other myth systems, though the qualities that make them unique demonstrate the priorities of of the civilization in which they arose.
Almost every ancient civilization had a creation story.
Several middle-eastern cultures have worldwide flood stories.
Etc etc.
The early parts of Genesis seem to focus on "this is why things are the way they are," and thus use symbols and an unspoken "way back in time before any of us were around" to convey mystical explanations of the human condition, etc.
Plus these stories were handed down orally, so focusing on a few memorable symbols to aid in memorization (the talking snake, the forbidden fruit, the flood, the tower to heaven) makes sense.
On the other side, the wording of the stories of Abraham and his progeny, of Moses and the exodus, and of the kings of Israel and Judah read more like documentaries, presumably because the facts are the most important thing being recorded. "Who did what when" is more important in these accounts, especially as they describe interactions with God, than some kind of generation-spanning morality tale. Not to say morality doesn't play a big part in the Old Testament histories, but the focus is on showing how real individuals failed to live up to God's calling to be His people.
The Psalms, Proverbs, Lamentations, Ecclesiastes, and the Song of Solomon are packed with symbols, but they serve different purposes.
Conjuring emotions, analogies, allegories, etc. are all potential uses for the symbols contained in these books, and it really comes down to each symbol's context as to what the author is trying to do.
For the New Testament, I don't treat any of the accounts of Jesus' life strictly as symbolism, though many of the events in the other gospels could be treated symbolically, even while believing them to be literal events, and John's gospel has a much more symbolic slant. He seems to have been trying to describe the larger truths surrounding Jesus and his life and ministry rather than writing a simple biography.
Acts reads like documentary, and the letters of Paul and the other apostles seem to be part instruction manual, part love letter, part philosophical treatise.
There is symbolism in the letters, but it is used to illustrate spiritual and moral points.
Revelation....sigh. Tonload of symbolism, especially involving the cultural symbols of the time. Given that one set of interpretations of the symbolism has already happened (the Roman Empire stuff) and that another set of interpretations has yet to happen, it remains to be seen how much of John's writing was literal (but limited to the vocabulary of the time) or symbolic (drawing on the emotions of the images rather than the images themselves).
I just think it's important to have a hierarchy of premises. 
