You shouldn't believe any predictions.

You should read any analysis that accompanies a prediction, and assess whether or not you agree with it. If there's no analysis - ignore the prediction. If you don't understand the analysis - ignore the prediction (this could easily be because the person making the prediction doesn't understand what they're doing).

Some people are better at analysis than others, but even then - they get it wrong sometimes. Do your own analysis as well. Just because someone has had good results in the past doesn't mean that they will in future - they could just have been lucky!