Understanding the market is a major undertaking where most investors will ‘not’ succeed not because they can’t but because either they have no interest or not enough time. Those that attempt to invest on their own have a responsibility to themselves to do the best that they can and if you are one of those you must take the time and work at gaining the necessary knowledge. You already have the interest or else you wouldn’t attempt to do it yourself.
To that endeavor one can learn, without too much difficulty, relative values of the stocks and sectors they want to buy. The best way for the average investor to begin the process is to study the economic cycle and the stock market cycle that adheres to it. They do not go up and down together. The stock market will move up or down first as the economy begins to recover or falter. In that cycle there are certain sectors that do better or worse at different stages of the economic cycle.
Understanding cycle and sector rotation will help the investor decide on which type of stocks to invest in and when to buy because valuations over long periods of time are stable but during the economic cycle, thus the stock market cycle, opportunities arise. When one group or sector falters and another rises you can find good companies that are at attractive prices compared to their long term valuation.
It is never easy but it is a skill that can be learned.