Vonnegut wrote:sometimes the multis just bust themselves.
LOL
But seriously, one thing that will clear you is both having premium accounts. They will see two different names from two different credit cards, and know that you are two different people if IP address is the only thing indicating you're a multi.
Also, don't play games together where you aren't on the same team and other random people can join. This is almost always where multi reports come from, people blatantly do not attack their other accounts and the collusion becomes obvious.
There's a few other tricks I think they do, but DiM is right, posting them would just help cheaters improve their methods.