You can't really as youtube recodes on playback. When you upload a vid it gets uploaded and stored in it's original quality but when you play it back through their player they recode the video down to a low resolution and quality before streaming it to you. As you can't influence their recoding settings you can't really do much about what it looks like through their player.
They did announce some time ago that they were working on imporoved resolution and quality in playback though and as all vids are stored in their original resolution and quality they will all look better after they switch to the newer player. They didn't say when though
If you want to do high quality vids you would try a freeware flash recorder like wink (
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) and then upload to rapidshare or the usual places liek that. I have used wink before for stuff like this. You can select a window or area of your desktop to record and you can even use comments and insert buttons in the vids. Sharing swf files means you can't fix the size to keep the text clear, but you can with compiled exes and passworded zip/rar/7z files cannot be infected with viruses
