Ask HN: SEO for web apps

Can anyone point me to a resource of good information for SEO as it specifically relates to a web app? Like a typical app, my site has a landing page which provides an overview of the site and allows you to login or sign-up, a "learn more" section with a more detailed write-up of what the site offers as well as FAQ and About Us pages. After that, its just the app. Aside from looking for a good resource for information (webpage, book) my questions are:

1. Is the landing page the only one I need to focus on for SEO purposes? (I'm thinking yes, because this is the page that will have all the linkbacks)

2. Should I use robots.txt to block the crawler from the URLs that lead directly to the app (which you need to login to use). Should I block anything else, like the images directory?

3. Should I try to point people to http://www.mysite.com or www.mysite.com or mysite.com? Should I try to pick the form that most of my linkbacks are in?

4. Is a Sitemap necessary for such a simple page structure?

btw, I've read this HN tread(http://news.ycombinator.com/item?id=119986), however the site that seemed to come off best costs $100/month. Looking to learn and do this myself.

Thanks.