When bitcoin price is going in a downward trend what's the best way to weather the storm?
you only have only 2 clear options.
1. hold
2. sell before the bottom and go to fiat
obviously if you are a trader then option #2 is for you. but you should make sure to sell soon because every second that passes it becomes late to sell and if you sell late you will be the last one out who got dumped on

Buy alt coins?
this is a terrible choice because history has proven that altcoins have a tendency to get dumped each time bitcoin goes down.