Personally I am looking at whether sentiment is decreasing or increasing compared to historical levels of sentiment. So for example if people start to talk more positive on Twitter about a coin or it gains more exposure I check that out more in depth. To do this I wrote an algorithm in Python, it seemed to work well past couple of months. In case you're interested to check it out, I wrote an in depth analysis on it on:

https://medium.com/@altcoinanalytic/beyond-conventional-indicators-a-study-of-twitter-sentiment-versus-crypto-prices-8870f5c788e5

Hi,
In order to keep track of the altcoin market I have created a report which calculates various metrics on current and historical Altcoin data. I am sharing this report regularly (at least weekly) by e-mail (for free). In case someone is interested please contact me in order to be added to the mailing list. The report includes (amongst other) the following metrics:

High - All time high of respective currency (in USD)
SD dec - Standard devation with decay of 0.9
SD mag - Standard devation with equal weights to relative to standard devation with decay
SD down - Standard devation of all negative returns (removes upside risk from risk measure)
Traded vol - Traded volume of respective altcoin
BTC cor - Correlation of altcoin with Bitcoin
frfl - Free float of altcoin

Additionally there are regression number on how much of return is explained by BTC movement and an indication of fear/momentum in the total Altcoin market.

Attached are screenshots of the report, let me know in case your interested.

Kind regards,