Who you are: What name do you want to be credited by, is there anywhere you want the post to link to? (Bit of extra publicity)
Source: Is this your theory or did you read it somewhere else? Credit is important! Don't just copy/paste someone else's work!
Theory: It's got to be good, and it's got to be interesting. "Superman is an alien" isn't a theory, it is just basic comprehension. "Superman is actually a magical clam" is a great outrageous statement, but you need evidence to back it up. The more convincing the theory sounds, the better it is. Perhaps you have evidence from the comics or movies of Superman gestating pearls or sleeping in a gigantic shell? Maybe you have compared the life cycle of a clam and found that it exactly matches up with Superman.
Also a good theory would be a few paragraphs at least, not just a low-effort sentence.
Further reading: Are there any more links on the internet where people could read up on your theory or aspects about it?
Email your theory to tinfoilfantheories@g