Hello Tony! I'm just a poster, so my answers are unofficial, but I think I can answer your questions.
1) Popping up in the general forum and saying, "Hi," is the way it's usually done, although posting in the Dogpile Forum with an arrogant demand for free labor is also popular.
2) TWCL doesn't e-mail comics (to my knowledge), but they do have a pretty snazzy spider that tracks updates of webcomics pretty quickly (considering it tracks tens of thousands of them).
3) The main site is a webcomic tracking service, and a large number of the comics listed are newspaper comics with a web presence. Here in the forum, the Check Out My Comic Forum is a place where comic authors can go, post links tot heir comic, and receive critiques. To my knowledge, since TWCL is a free site/service, Ash prefers that the actual author (or copyright holder) posts his/her comic on the List and in the COMC forum.
4) You didn't ask this, but everyone eventually does: Webcomic rankings are agregated by an arcane formula known only by Ash and the President of Qatar. A team of Lichtensteinian mathematicians did determine that the formula considers update frequency and number of outlinks from this site. Shortly thereafter, they all disappeared in an "accident" involving a particle accelerator and a swarm of Uruguayan murderbats.
_________________Casual Notice--commentary, comics and an appreciation for snappy hats.