The first step would be to ask wallet developers to switch the default unit:
https://bitcointalk.org/index.php?topic=598082.0If this gets done, then online wallet providers will probably follow.
Finally, exchanges and payment providers will also start using what their customers' wallets are using.
If Bitcoin Core would implement these changes it would go a long way. They just need to see that everything is advantage and not much disadvantage here - just needs to be done!