My "bottom-fishing" principle is as follows:
Buy in parts: Don't buy everything at once; buy in several batches to reduce the risk of the market potentially continuing to decline.
Observe the overall environment: It's best to wait until the market sentiment stabilizes or the major indices start to rebound before considering entering the market.
Set a stop-loss point: If losses reach a certain level, promptly cut your losses to avoid further losses.
Look at the fundamentals: Choose those good companies that have been excessively sold off due to market sentiment but still have decent fundamentals.