Tip: If you update a page, or add a new page to your site - then put a direct link to it from your frontpage for a month. Google will see that the frontpage has changed a bit, find the url, and update accordingly. A "News" section with static links is ... nice - both for your users, and for the search-engines. Could also be an idea with an rss-feed.
Note: Google deepcrawls sites about 1 x month if they think there's new contents somewhere
