I hodl alts that I think will not follow the fall and lose value. Which alts? It changes constantly depending on the state of the every project in the time the bear market happens. A lot of people speak about hodling XEL no matter what.

If the market is going down and you think it will go even lower, you can convert whatever you think will lose value to USDT (tether) - then call the bottom and than buy back your positions. That's what I do. Can something go wrong? Yes, it's speculation - many things can go wrong. Also, most alts tend to bleed more then btc and eth when the market is going down.

Trading Discussion part of the bitcointalk forum may be a better and more appropriate place to ask questions like these - you may get more answers as it is trading discussion only.