Keep it on MEW and you do not have to do anything. If you keep it on an exchange, be sure that the exchange supports the fork.
You are not aware of this fork in fact. It's a hardfork and nothing to support by the exchange. Keeping in MEW is okay but if someone is using qt wallet, he must have to update his wallet for continuing with the new chain. Otherwise, he will not be able to send eth to others. But there is nothing to fear at all.