To establish causality you need to show three things–that X came before Y, that the observed relationship between X and Y didn't happen by chance alone, and that there is nothing else that accounts for the X -> Y relationship.

How do you check for causation?

Run robust experiments to determine causation. Once you find a correlation, you can test for causation by running experiments that “control the other variables and measure the difference.” Two such experiments or analyses you can use to identify causation with your product are: Hypothesis testing.

What is the best way to give evidence of causation?

Experiment. Randomized experiments are the best way to identify causal relationships. Experimenters control the treatment (or factors involved), randomly assign the subjects, and help manage other sources of variation.