SEO Title Tag plugin

I have been on the prowl for several ways to optimize our blog. I have found quite a few things that are handy but cant seem to figure out how to make it work properly. The instructions make it simple, I follow and then there is still an issue.
– URL’s: We’ve changed the permalinks to display the type of URL’s that we want to display. We’ve d/l a few plugins that were supposed to help but cannot figure it out. All of the URL’s and Titles appear to display in a breadcrumb format. We’ve changed the permalinks and installed SEO Title Tag Plugin to override the old title tags but with no luck. Any advice on how to get this to work? Is there some code that needs to be adjusted?
– We contacted the programmers on how to prevent have 4 different URLs pointing to the same content. Is there anything else we should do on this front?
– What other SEO enhancements have you done and do you recommend doing to achieve top results in the search engine results pages?
– Are there any plugins that allow you to display your posts and or pages in a short 2-3 sentence snippet with a click here link to read the entire post or page? (i.e. if we use our blog home page to display the most recent posts and pages, can we only show snippets of each so that the page doesnt scroll forever?

Any suggestions on optimizing our blog for SEO purposes is greatly appreciated. We’ve done a ton of reading and found some great resources, but we would like to hear from people who have SEO’d their blogs with success and what they did to achieve success.

Thanks.