Miran Pirner posted the thread about this but the link died, I went on the site and found the updated version on it so I copied on here. 
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When posting to Youtube the first thing to remember is that it will make your video look worse. No matter what. Youtube is compressing your video and compression makes things worse. Period. However, if you follow some simple rules, you can minimize this worsening, or 'Youtubeification', to the point where it is not noticable. Read on.
1. Shoot the highest resolution and the lowest compression possibleThere are about a million different video cameras on the market. There about 500,000 different video formats that they shoot in. Ok, I exaggerate, but your choices in shooting formats are immense. Some of these formats are better than others. To achieve the best results on youtube, choose the highest resolution and the lowest compression possible. For resolution, you should pick an HD camera (1920x1080 or 1280x720 pixels) over an SD camera (720x480 or 720x576 pixels). As far as compression goes, you want a camera that has the biggest file size possible once it gets onto your computer. Also, if you can see compression artifacts in your original video, these artifacts will get worse on Youtube. Ok, so you probably already own a camera and maybe its not perfect for Youtube. What else can you do to get better quality?
2. Use a Tripod!That's Right! Using a tripod makes your video look more professional and it helps minimize the compression problems associated with Youtube. Why is this? Video compression is based on motion -- the more motion in the frame, the more work the compression has to do. When you shoot hand held, every frame is a little bit different which makes a compression algorithms go crazy. When you use a tripod, the image only changes when something in the frame moves which is a relatively small change. Or it changes when you pan or tilt, but these changes are smooth and predictable enough to be easy on compression.
3. Have plenty of lightCompression is based on detail. If things are dark it will be harder to achieve nice compression. This can be as simple as opening the blinds, turing on a lamp or going outside. In general, bright is better than dark for compression.
4. The secret ingredients to encoding for Youtube: at least 6000kbps h.264, 640x480, Multipass encode, deinterlace, letterbox. No matter what you use to encode your video, these magical settings should insure a clean version to post to youtube. I personally use Quicktime Pro. So I will go over these particular settings here:
The Quicktime Pro Export Menu
Selecting the h.264 codec and settingsSelecting the frame size, deinterlace and letterbox settings
* h.264 is the most modern codec available and is able to compress video in the best looking way possible.
* At a data rate of at least 6000kbps the compression should be virtually invisible for a frame size of 640x480.
* The frame size of 640x480 is chosen because this is the native frame size that Youtube displays
* A Multipass encode checks each frame at least twice to ensure that it is encoded the best.
* If you shoot on an interlaced format, you must deinterlace because computers are a progressive format. If you don't, you will see the so called 'mice-teeth' effect.
* If you shoot on a widescreen format(16x9) then you must letter box your video because youtube is in a 4x3 format. If you don't your video will be squished
* One more tip: Try to get as close to the 1 gigabyte files size limit as possible by increasing the data rate. Don't go over board though. A 10 second clip won't ever be that big
There. Now you know the best settings to get the best out of Youtube. As a public service I have posted below two examples. One with the right way of doing things and one with the exact opposite. Enjoy!
This clip was shot with a Sony Z1U. It is a clip from my upcoming documentary "Legacy of the Great Aletsch"
