Steem blockchain is in a league of its own in the cryptocurrency world. It's one of the few cryptocurrencies that is sustained by its community using DPOS algorithm.
I like to think of Delegated Proof of Stake (DPOS) as technological democracy. Just think about how many asshole bosses there are out in the world. Have you ever wanted a system in which you, the employee, get to fire your own incompetent boss? Well, there is a new system that is very close to the reality of employees getting to fire their own managers. It’s called Delegated Proof of Stake. Source
In simple terms, when you vote for a Witness on the Steem blockchain, you're doing your part to sustain the blockchain. Read more about the process on Hackernoon here: https://hackernoon.com/explain-delegated-proof-of-stake-like-im-5-888b2a74897d
I won't be making another post on who a witness is or why they are important to the Steemit blockchain. I'll be dropping snippets and links to some posts that did justice to that.
Who is a Witness?
A witness plays a crucial part in how the STEEM network functions. Some people might not be aware of this, but Steemit is just a fancy web interface on top of a large network called STEEM, which operates remotely similar to Bitcoin.
Witnesses have many tasks. The first and foremost is to produce blocks (thus process transactions), the second most important is to produce a price feed, which is how STEEM Dollars are always worth 1 US Dollar in STEEM (using the 7 day exchange).
Source
You an read this guide by 
How to choose a witness?
There are many factors to consider when considering a witness to vote for and it can be confusing to come up with answers.
Due to the nature of Steemit, it is attracting people who are not necessarily familiar with cryptocurrency concepts and the difference in the way that mining works can be confusing even to those who are familiar with conventional POW (proof of work) or POS (Proof of Stake).
There is understandably a lot of confusion in the community over the role of witnesses as well as who to vote for. There is also inconsistency in the information that witnesses and witness candidates provide to potential voters.Source
You'll find possible questions to ask a potential witness in this post by 
How I chose my witnesses
Everyone on Steemit can vote up to a maximum of 30 witnesses. At the moment, I have 15 slots remaining. You can check that here: https://steemit.com/~witnesses.
You can decide to choose your witnesses yourself or assign someone you trust (a proxy) to help you in the selection process. Personally, I don't like this option. I want to participate in the selection process based on research and personal conviction.
That been said, all the witnesses on my list have added to my growth on this platform in one way or the other. I believe that the least I can do is to support them so that they can continue to pay it forward. Their selfless service on Steemit blockchain earned them my vote and I'll continue to support them as long as they remain a dedicated witness.
My top 15 witnesses on Steem Blockchain
Check out their profiles and see why I voted them as my witnesses.
So far, they are doing a great job and are yet to disappoint me. I still have 15 votes to go.
To sum it up, when you vote for witnesses, you are helping to secure the Steem network. You can also remove your votes anytime you want.
Visit this link to vote for your witnesses now: https://steemit.com/~witnesses