Ways to make sure an article gets indexed?

Hey folks,

I have been doing article marketing for a while and have submitted a few hundred unique articles to various sites. Today I did some searches on my titles and realized that on some of these sites, many of these articles have never been indexed by Google. (We are talking unique content, so they're not getting thrown out for being dupes or anything.)

On EZA the % that had been indexed was very high, but on other reputable sites many articles appear to have been missed by Google.

Anybody have some good methods for making sure an article gets indexed? I've tried Digging some articles in the past with mixed results; Digg bookmarks can fall off the upcoming stories pages pretty quickly if they don't get votes, and then Google may never notice them.

On my own sites, I use sitemaps etc. and pretty much everything gets indexed.

So, what do you guys do to make sure a new article you've written, or a new page on your site, gets indexed?

Thanks!