Whether or not you should care how well Google indexes your weblog is an interesting question, but one which would take more time to cover than my current attention span. However, if you do want to rank as high as possible, I can tell you one thing you should not do: use underscores to separate words in the path and filename. I’ve seen him say this before, but I always seem to lose track of the quote (so it’s a good thing I have a blog, to store things like this): according to GoogleGuy, the Google employee who posts at WebmasterWorld:
If you use an underscore ‘_’ character, then Google will combine the two words on either side into one word. So bla.com/kw1_kw2.html wouldn’t show up by itself for kw1 or kw2. You’d have to search for kw1_kw2 as a query term to bring up that page.
Translating from the “no real words” language of WebmasterWorld, that means that /underscores-are-bad-mmkay.php would match a search for underscores, or for bad, or for mmkay, or in the case of a blog that uses the title in the URL and in the page, would reinforce the importance of each of those words, while the filename this entry will get, underscores_are_bad_mmkay.php, only matches a search for underscores_are_bad_mmkay.
Personally, I’ve never been very interested in search engine visitors, and I lost most of my interest in search engine results when I dropped out of first place for Phil, but if you blog in a way that makes you want to be highly rated in Google, and you are planning a major URL change anyway, there’s no sense throwing away ranking by using underscores, when hyphens are nearly as pretty, and give you separate words in Google’s eyes.