How to make the most commonsense plan work

The most commonsense plan is " Buy low, Sell high ". How to make sure that this beautiful plan work ? The stock must belong to a profitable company with cash reserve and, preferably, a market moat. Look at the 6-month to 1-year graphs and buy only at the bottom prices. Use money that you don't need to spend and the stock can ride up high, at any time later.