QUESTION # 1:
You have to be a YouTube "partner", which more-or-less means you are either
a film / video creator or producer, an artist (musician, singer, comedian, actor),
a media company, an advertiser, a broadcaster, a person of great significance
(like President Barack Obama) or somebody with a special project or mission
(like Shawn Ahmed and his Uncultured Project for the children of Bangladesh).
http://youtube.com/UnculturedProject
But that is not enough to become a "partner". YouTube has even more criteria:
-- You create your own original videos (meaning videos nobody else has done)
-- The content is 100% yours (there aren't any elements that belong to others)
-- You own all of the implied copyrights
-- Your videos are viewed by thousands
-- You upload videos on a regular basis
-- The videos are suitable for all viewers
-- You are a resident in one of the 23 countries where YouTube has local sites
-- You can prove you are 18+ years old.
Generally, YouTube will not consider you unless you've got some combination
of "subscribers" and "videos" that when multiplied together can easily surpass
10,000 channel views. Thus, you would need, for example, something like 800
subscribers and 20 videos or maybe 500 subs and 30 vids -- as well as a total
view count of considerably over 250,000.
Only after you have met all those conditions and been "approved" by YouTube,
they will give you all the special tools and codes which will enable you to have:
-- an 875x75px banner for your channel, 875x150 if you're "corporate" branded
-- a mini-banner beside each played video
-- your channel-page video on "auto-play" ◄
-- "special" videos more than 10:59 long
-- automatic higher quality to your videos
-- unique skins/sizes for the video player
-- an unlimited choice for video thumbails
-- extra boxes: links, bulletins, contacts
-- another picture for your "connect" box
-- option of animated GIF for background
-- being at the very top of search results
-- the possibility of earning "ad revenue"
-- the light-bulb "watch at night" feature if your "account type" is as a "director"
-- a "More From" section which overrides the regular "Related Videos" section
and featuring only your uploaded videos.
If you wish to know more, go to the top righthand corner of any YouTube page,
click "Help", and type "partner" in the searchbox. Or click on either link below:
http://help.youtube.com/support/youtube/bin/topic.py?hl=en&topic=12632
http://www.google.com/support/youtube/bin/search.py?query=partner&ctx=en%3Asearchbox&client=&hl=&cx=&cof=&adkw=&search_type=hc_help
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QUESTION # 2:
It's relatively simple choosing which video you would like as the
"featured" video on your channel page:
1 -- click on "ACCOUNT", alongside the ▼ at the top of a page
(you'll see a new page with black titles & lots of blue sub-titles)
2 -- click on "EDIT CHANNEL", the 2nd blue title to the far right
(you'll get 3 different blue sub-titles including "Channel Design")
3 -- click on "CHANNEL DESIGN"
(you'll get a new page with nine colour combinations at the top)
The very next set of parameters asks about your featured video.
4 -- click on "FEATURED VIDEO"
(the bullets immediately below will become brighter and prompt
you to choose either your most recent video or any other video)
5 -- click a BULLET
(if you choose "Video URL", you will get a new rectangular field
prompting you to copy-&-paste the complete URL of that video)
6 -- paste your VIDEO URL
(you have to afterwards make sure your change will take effect)
7 -- click on "UPDATE CHANNEL"
(it will be on the stripe just above the nine colour combinations)
If you want to double-check it for yourself, here is the complete
URL address of YouTube's "Help" reference, followed by its link:
www . google . com / support / youtube / bin / answer . py ? hl = en & answer = 97392
http://www.google.com/support/youtube/bin/answer.py?hl=en&answer=97392
Believe it or not: You can actually change that "Featured Video"
from right here inside of Yahoo! Answers by clicking on my link
below, which will bring you right to YOUR VERY OWN channel
set-up. (YouTube may prompt you to "sign in" first):
http://www.youtube.com/my_profile_theme
Be aware that it can sometimes take YouTube up to 6 hours to
properly update your channel page.
I hope that my step-by-step answer is somewhat helpful to you.