I have found that anytime you are looking at a specific domain/sector then you want to see it from as many angles as possible. For volatility, there are a huge amount of indices on the CBOE website that you can overlay against each other. Volatility in some asset classes will lead or lag vol for other asset classes. You can also keep an eye on the spread between the front month and second month future VIX contracts. As we approach the low end of the range in the VIX, we can look at vol from a bunch of different angles to get an idea of what might happen.