I'm often asked "how do I start streaming" and I have THOUGHTS and ADVICE! And I'm going to share ALL OF IT ^_^
JUST START STREAMING
My first piece of advice is: Just Start Streaming.
Don't put it off. If you really want to start, make it a priority. At the minimum commit yourself to 2 regular streams a week. Keep it regular and only as long as you enjoy. If you need to take a day off, do so, but come back again.
Streaming should become a habit, and one that you actively enjoy (if you don't enjoy it, don't push yourself into doing it; find another aspect of gaming content creation that excites you).
When you start you will be streaming to no-one, and that's OK! It will give you the opportunity to practice streaming with no pressure. It's very hard, but don't let numbers worry you. Walk your own path, not anyone else's.
Find a community and hang out in streams together. Host other people who have similar interests to you. DON'T advertise yourself in other people's stream. This is bad manners and will get you banned in most other streams. Treat the connections you make like business networking; be respectful and build a connection that benefits both of you.
Onto the technical!
When you start out, don't feel you need to go out and buy all of the expensive things. Streaming can be daunting when you're starting out and the pressure of having to "succeed" can make it overwhelming. At the very minimum you should have a reasonable quality microphone and a computer that can handle running both the game and the streaming software (such as OBS).
Start out by recording your gameplay and then watch your replay. Do you talk enough? Are your sound levels balanced? Is your voice clear? Are chat windows hidden? Make corrections and practice until you're happy.
Then do a few test streams (but don't let people know you're going live). Test the same things, but also check that your stream is reasonably smooth looking. Don't forget you now have to take into the quality of your Internet upload and how it affects the quality of the stream. Watch your playback on Twitch (or Mixer or YouTube) and make sure the quality is acceptable. Adjust your settings as required (and then delete the test broadcasts).
If your Internet is slow (ADSL or low quality fibre) you may need to make some compromises with quality in order to stream, but STREAM ANYWAY. Don't put it off waiting for better Internet (or tech).
If your Internet is very fast, don't stream above 720p 30fps 2000 bit rate; people with slower Internet won't be able to watch you as your stream won't have a guaranteed down-sampling (unless you reach partner).
DO I NEED A FACE CAM?
It depends :D
Your channel must be active an appealing when someone drops by to see what your about. Some of the best streamers I know don't have a face cam, but they're able to chat continuously when people drop into their stream so that visitors know that there is activity.
If you have a face cam, you don't need to be quite so active because people can see you're a real person immediately. But unless you interact with people, they're not going to stay.
Other options are a cute pic to represent you, an animated face replacement (though that does need a face cam for the animation).