Well for now until Steem SMTs launch, The easiest way to start your own cryptocurrency is to create a erc-20 token on the Ethereum blockchain, this is a pretty simple process that consist of finding an appropriate smart contract for your token online (you can find hundreds by just googling) or creating one yourself if you know how to code.

There are a few types of contracts to pick, like ICO contracts that distribute the tokens automatically to the buyers, a basic creation contract that just creates the tokens and gives them to an address to them be airdropped, gaming contracts, name it.

After you have your contract picked, you just have to "upload" it to the Ethereum blockchain which cost around 25$ and you are pretty much good to go. Its pretty easy and its the reason to why there where so many ICO lately.