For me, I did it by joining in bounty programs that either use Ethereum as a mode of paying or rewarding people who joined the project. However, the rate of those projects are getting less and less by the moment, since many projects are more so focused on starting up their own coins that using other established coins to be used as payment. Or, I also gain Ethereum by trading the coins I gained from bounties after their release to the public and registration to trading and exchange sites. I do that since I am more confident holding coins that are already established as compared to newer ones.