Submitting random articles from favorite sites (TechCrunch, Ars Technica, TorrentFreak, etc.) as soon as they're published (i.e. before anyone else), would probably get you a few thousand Karma points in a month or two.

From my point of view however, getting good points on a comment is a lot more satisfying and worthwhile than your general Karma count (once you're over the various thresholds).