Well first you would have to discover that it has a community at all, because surprisingly many do not.

There really is no sure way to tell if there is a strong community supporting it. However, there are some characteristics and metrics which are probable indicators of sustained support. Some of that is going to be based purely on observations while other indications are purely intuition and experience based.

A more basic and obvious measure of the strength of a crypto community is the trade volume of that coin. If a Coin has very little trade volume then obviously it’s “community” isn’t doing a very good job supporting it. The backers of a coin must also practice what they preach, and if they do not, that’s the easiest way to rule out a supportive user base.

Another good indication is to examine the network of platforms and exchanges and various other services that make up the framework and logistical backend of the coins usage.