www.anymeeting.com before discovering www.livestream.com and Google+ Hangouts On Air.
In the early days (only a year or two ago) I relied on Quicktime Broadcaster as there wasn't much else on the market that was as reliable (and free). The problem with using this application, is that it wasn't the easiest thing to use. It was only until I was asked to help set up a livestream to go between one teaching space to another (between two different floors in the Arts Tower) that I discovered livestream. The academic I was working with suggested we try using it as QuickTime broadcaster wasn't 'playing ball' that day. It didn't take long for me to realise what an amazing and powerful product it is. After setting up the live stream that day I went and signed up for a free account straight away. I have never looked back since.
Livestream isn't the only thing out there, there are other products such as www.ustream.tv, www.justin.tv, as well the recent Google+ Hangouts / Hangouts On Air. This blog isn't about recommending which one to use, but more about outlining the best practices in terms of livestreaming as a result of doing so over the last 12 months.
Live streaming is very easy to do and anyone with a computer, mic, webcam and good network can do it. One thing I would note is, always make sure you are connected to a wired network. With live streaming it is important to make sure you have the best chance of the whole stream being stable. Taking risks by streaming over a wireless network is in my opinion to high. If you are having a video chat with one or a few people, then go ahead use wireless or 3G (I do). In these instances if the connection goes, people accept it.
If you wanted to put together a stream of an event of 300-500 people in an lecture theatre, then it requires much more then just a computer, webcam and mic. Recently we livestream'd our in-house Making the Most of Google event and for this we fed two cameras (one 'manned'), lectern computer, audio from PA system, via a vision mixer, scaler and distribution amp into a mac laptop. It was quite some set up, but it all worked like a dream. For the stream, the end user could see and hear the the presentations given, and for us we were able to follow the presenter with a tight camera shot, switch between camera sources for questions and overlay titles of who was presenting and what it was about.
Tech info: For those interested we used Sony 2 x HXR-NX5E's cameras, Data video SE-5000 vision mixer, Blackmagic H.264 Pro-recorder and Apple MacBook Pro.
If you don't have such kit or are wanting to do something less 'full on', I would always suggest using a webcam other then the one that is integrated (unless it's a livestream of just you). Having an external webcam will give you the flexibility of where you can place the camera source in relation to your computer. Streaming good quality audio is not easy, but again an external microphone should provide better quality. Either that or a USB table mic. We use Clear One Chat attach 160's. They are just plug and play and provide excellent quality.
So to summarise, if you haven't already tried it.... give it a go and stream something using any of the products I've mentioned above (or even something else - let us know what you've tried in the comments!). Always connect to a wired network when streaming and if you want better video/audio quality, invest in external hardware. When deciding which live streaming product to use, use one that supports an array of mobile devices. The live streaming products which only work accessing it via on a computer end up limiting the amount and ways in which people can view your stream... which isn't necessarily what you're after