They always say: Don't trade what you can't afford to lose.
Past that, just don't get too emotional. Don't chase momentum/price. Buying when the price is dropping is better than buying when the price is rising. Those are my general rules, anyway.
then you have the same strategy with me. Buy low sell high
don't buy high sell higher, risky.
I won't lie, when I've "missed the boat", I have bought high and sold higher. It works out in strong rallies, but certainly preferable to buy on the way down or near the bottom.