1) Build a diversified portfolio: Beginners put all their eggs in one basket while a professional would know what to do exactly. The smarter approach is to build a diversified portfolio based on market cap, tech and team behind the project. This decreases the risk of incurring losses.
Irrespective of all this yet when the bear market comes, it affects all the altcoins so what was the need of diversifying in the first place if your investment capital isn't protected from this. Diversifying in cryptocurrency was only favourable when the market is experiencing positive return as the chances of profiting more increases although in the period were market price is declining it because a negative and wrong decision to make.
You're fall better diversifying to other assets outside cryptocurrency since they're not related and your investment capital will be protected from a downward movement in the market.