For a long period of time i've been submitting my updates to Google and other search engines right after they appeared at my blogs. But that's not good if you are dreaming of high PR.
You must know what PR (Page Rank) is. If not, i'll write more on this topic these days, right now you can simply check Wikipedia. The thing about PR is that it updates quite seldom, sometimes it can take up to 4 months. And as your pages get their PR based on inbound links, they maybe checked only after long period of time, if the page was indexed before you submitted it to directories, etc.
I strongly suggest you to submit quality new articles to Reddit, Digg, etc, wait for some backlins a day or two, and then submit it to Google.