You can never reduce the risk to 0% obviously but you can reduce it by learning TA (technical analysis) and FA (fundamental analysis). Technical analysis is the study of charts and patterns in said charts, fundamental analysis is being smart about what's going on (if some news will affect the price or not).

These are all the tools we have, unless you have insider information of course. I don't think it's viable as a job, most people lose money. Just wait for big dips, buy them and hold it.