I assume this is a rhetorical question, since you are perfectly capable of doing a search for "the scientific method" on your own.

MWI has not led to any verifiably-correct predictions, has it? At least not any that other interpretations can also predict, and have other, better properties.

You use the hypotheses to make predictions and design experiments. Then you carry those out and see if they support the hypothesis.

Or is this one of those rhetorical questions?

Okay. I have a hypothesis that the rain is controlled by a god called Ringo. If you pray to Ringo and he listens to your prayer it will rain in next 24 hours. If he doesn't listen it won't rain. You can also test this experimentally by praying and observing the outcomes.