The next best thing to guessing

One way to solve a problem.

A person will try something, get it wrong, learn from the mistakes, try again, and hopefully eventually get it right.

Many great ideas and inventions were devised through the process of trial and error.

trying something untill you get it right

The story of my life.

A systematic means of determining a solution to a problem, often involving a large amount of time; often involves eliminating possibilities.

when you mess up repeadedly until you do something right

To do something by trial and error means to brute force it. Just mindlessly trying different combinations of something until you get the right result.