To make a long story short: you can’t mine steem.
Or, to be more precise, you can’t mine steem anymore. In the early days of Steemit this was possible, but as the miners got the quirks of the algorithm and conquered the mining queue with just 2 or 3 players, the general consensus led to the elimination of the mining entirely.
The Long Story
You can get steem in 3 ways:
- by blogging
- by buying it on an exchange
- by supporting the network as a witness
What Is A Witness?
The functional role of a witness is described here, but before jumping to that link, please spend some time here to learn about PoS.
PoS (Proof Of Stake), as opposed to the more popular PoW (Proof of Work) it's the underlying mechanism of the Steemit consensus. If you want to become a witness, you have to own (or have invested in you by other people) a certain amount of Steem. Meaning to have some stake in the network. It’s all described in the white paper, but if you don’t have time to read it, it’s ok, I’l try to make that in plain English below.
How Do I Get That Stake?
Please refer to the way you can get Steem above: you can blog your way into it, you can buy it, or you can get it in the form of votes from other people.
So, there are two types of votes in the Steemit network: a vote that gives people money (to put it shortly) and a vote that gives people power as witnesses. The votes that give money are the ones you give to each post or comment, while the votes that give people power are the ones you can give to witnesses here, on this page.
How Much Stake Is Needed To Become A Witness?
To be in the top 100 witnesses, you need around 198 million vests invested into you. Which means around 100k Steem. At the current price of Steem, which is around $2, that means around 200k USD.
What Machine Do I Need For Maintaining A Witness?
RAM is crucial, as part of the blockchain is held on RAM. Otherwise, any decent machine will do it.
How Do I Make People Vote For Me As A Witness?
Be useful to them and they will vote you.
I Don’t Know Which One To Vote, But I Have Some People I Trust, Can I Delegate Them To Vote For Me?
Yes, it’s called proxy witness delegation and you can do it on the same witnesses page.
I'm a serial entrepreneur, blogger and ultrarunner. You can find me mainly on my blog at Dragos Roua where I write about productivity, business, relationships and running. Here on Steemit you may stay updated by following me 
https://steemit.com/~witnesses
If you're new to Steemit, you may find these articles relevant (that's also part of my witness activity to support new members of the platform):