I love the sense of freedom I have: I'm not beholden to any particular person. If someone rubs me the wrong way, it's extremely easy for me to not work with them anymore.
I love the variety of assignments.
I love how easy it is to switch into new specialties by underbidding others to get a kind of 'unpaid internship'.

Tips

For freelancers

Be aware that there are clients who will ask for help debugging code they're writing but (for some reason) don't know how to check the documentation for the libraries they're using, and/or don't know how to ask for help on Stack Overflow.
- One guy I helped with a single line of code I found with a few minutes of searching Google.
- Another guy asked for help with Pandas and I spent a ton of time trying things and writing up a non-Pandas solution, and then after he accepted my answer I asked for help on Stack Overflow and got a 1-liner working answer in about 5 minutes. So I should've just immediately asked on Stack Overflow once the client had given me a minimal example.
- This kind of "be the middle-man for people who don't know better" was basically the entire basis of the business of Westlaw Court Express.
- These clients probably also make good first clients for people just starting on Upwork.
If you're starting out and bidding low to build up positive reviews, don't waste your Connects on job postings that are asking for "Expert" developers.

...

Start the cover letter with something a little formal like "Hello," to signal that you mean business.
- (As opposed to saying "Hey," or "Hi,")
After two line breaks say something that inspires confidence in the client, like "I can do this." or "I can do this quickly."
- (As opposed to hedging yourself by saying something like, "I should be able to do this" or "I think I can do this").

If you don't give enough detail about the scope of the project, you may very well have freelancers refrain from submitting a proposal because they don't want to spend their Connects to submit a proposal only to find out that you are expecting far too much work for the rate you're willing to pay.
- Real example: Someone posted that they wanted a freelancer to create "Python multiple-choice questions", and that they were willing to pay "$100". I (as a freelancer) only had four connects remaining for the month, and so I said to myself, "I don't want to spend two of my last connects only to find out this guy wants 100 or 200 in-depth questions."