Good (and recently updated) article for help in setting up Titles and Descriptions for your sites.
Not mentioned in here, but similar thought for Title should go to your main heading. Your page should have only ONE <h1> heading tag, and that should concisely describe the content of THAT page.
It can be a tricky fine line to get good titles and headers that accurately describe, while being both understandable to both humans and search engines, while not being too large.
If you find yourself struggling to come up with one main description of the page, it may be time to break it out to sub pages. Done properly this can help your search rankings, as now instead of being a page about, say 3 topics and that one topic having to share weight with the other two, now you have a specific page to the one topic, giving it higher authority on the topic. (compared to being on a page with 2 other topics).
Just some ideas I thought I would pass on as I was reading updates on Google's blog. (This forum and plowsite came to mind while I was reading the other topic, that google is adjusting to possibly penalize sites with excessive ads at the top of the pages)