Alan Bandy has posted seven tips for interpreting symbols in the Apocalypse, i.e. the book of Revelation. His seven tips are.
1. Recognize the symbolic imagery associated with the description of people and beings, colors, numbers, institutions, places, and events.
2. Look for interpretations of those symbols within the vision.
3. Determine if the symbol stems from an allusion to the Old Testament.
4. Compare it with other apocalyptic writings to see if it is a common symbol with a relatively standard meaning.
5. Look for any possible connections between the symbol and the cultural-historical
6. Consult scholarly treatments of the symbol in commentaries and other works.7. Remain humble in your conclusions.
For a fuller explanation see the post here.