IDEX is a semi-decentralized exchange for ERC20 tokens on the Ethereum blockchain. There is a plan to decentralize the exchange further in a three step process. Currently, everyone can contribute to this efforts by running a tier 3 staking client, and thus providing the trade history of the exchange to the customers.

Doing so, one will earn a percentage of the trading fees from the IDEX exchange. The more IDEX tokens one owns, the higher the uptime of the staking client, and the higher the volume of the exchange, the more you can earn. A calculator of the possible earnings can be found here:

https://docs.google.com/spreadsheets/d/1DGKTJATIiUqAOjw6gfk5A_O0kqV-jH4IxpGI14jzdxg/edit#gid=0

Assuming an exchange volume of 1 Million $ a day, one can currently earn around 3$/10'000 IDEX tokens staked. With the current price of 0.025$/IDEX, this corresponds to a return of capital of 13%, which is quite good. Increasing trading volume might boost this number in future even further, but it will also increase the price of the IDEX token, as more people will want to join the staking and earn return of capital.

In order to stake IDEX on a staking tier 3, one needs to own at least 10'000 IDEX tokens. You can get IDEX tokens by exchanging ETH to IDEX on the IDEX exchange itself:

https://idex.market

After owning 10'000 IDEX tokens on a wallet, one can run the staking software provided and described here:

It is recommended to run the staking software on a virtual private server (VPS). In my opinion, this does not help the decentralization of a project as much as running it on a private computer at home. Furthermore, even the cheapest VPS cost a couple of dollars a month, which is currently more than you can earn with staking 10'000 IDEX tokens.