I assume you're talking about the test where the researchers infer the likely fate of the marriage by tracking the "trajectory" of a 20-minute-or-so conversation. My impression is that proper interpretation of the test requires training.

Gottman has written popular relationship advice guides based on his research; I'd recommend that anyone interested in maintaining the health of their current relationship have a look. His advice makes the assumption that certain correlations he's observed are causative, but that assumption seems reasonable for the most part. Research into the actual causal effect of his suggested interventions is ongoing.