I have worked as a freelancer and I have hired them as well. This list is for Freelancers. I will make a list for people that want to hire a Freelancer at a later point in time. If you are interested, please follow. So, let's jump right into it.

So you are a freelancer or want to become one. But where do you start? Here is a list of things you should and shouldn't do.

DO:

• Find your skill set. Nothing is worse than taking up a job and realizing you are not capable enough to do it. If you are not sure about your capabilities in a branch, do not take the offer. It will only lead to bad ratings and disappointment.
• Manage your expectations. Don't go into freelance thinking it will pay six figures. It is very hard to get a job in the beginning. As soon as you deliver your first contract it will become easier.
• Deliver. Trust me. Trying to scam on freelancing websites and networks is dumb. It usually does not yield any money and you will have some boys in blue knocking on your door.
• Deliver on time. Or even early. It is worth it. Your ratings will rise dramatically. Everyone loves a decent product delivered ahead of schedule. 

DON'T:

• Be an overachiever. It never paid off in my experience. You deliver more than your customer asked for and your ratings start to plummet.
• Ask for money. If you don't like a contract or offer, don't take it. It puts you in a bad light and the client in a bad mood when you ask for more money upfront. Small negotiations can be made but I advise against it in the beginning. Deliver your work, get paid. Simple as that.
• Deliver a product if it is bad or unfinished. It will ruin your reputation more than telling the client that you need some more time. If it has come to that situation, tell your client that you need some time. It usually helps if you offer them to drop the price. Then they will gladly forget that you didn't deliver it on time. And they won't put a bad rating on you.
• Be up your own ass. Or be rude to the client. Nobody likes that. It usually just ruins your chances of getting the offer.

This is by no means comprehensive. This is just my experience on Fiverr, Upwork and other freelancing sites. Hope this helps someone.

Cheers :)