a few Varnish intro questions

[Jason S-M]

Hello All,

I was told about Varnish today. I have a growing Apple fan website that as more and more videos get added my thought is to keep the most popular videos in cache.

The machine this site is running on is CentOS 5.5 64 bit, Apache, PHP,
MySQL 5. It is a dual core machine with 12gb of RAM, max is 16gb and I
will max it out over the next month or so probably as I find good
deals on 4gb DDR3 sticks.

The site's size will be about 300gb (about 60gb now) I have LVM
running with 300gb allotted to /var/www/html. I have a MySQL backend that stores paths and data about the video's, the videos themselves are housed on the filesystem.

Can anyone provide insight on setup and optimization of Varnish?

I have some confusion.
1. Looking at: http://www.varnish-cache.org/docs/2.1/tutorial/putting_varnish_on_port_80.html

So I have to run varnish on 80 and my site on an alternate port (8080 as example)? Or do they both run on port 80? 

2. Apache listens on my public IP and Varnish should too, correct? or do I use 127.0.0.1?

3. I must make additions to vcl_recv I assume to cache what I want? 

4. Do I have to make changes to my web pages to add meta-tags to trigger Varnish?

Best,
-Jason

PS - I see 2 addresses for this list: varnish-misc at projects.linpro.no and varnish-misc at varnish-cache.org a ping shows different IP's although I suppose that would not be a definitive answer.