As I've been posting here on LessWrong for a few months now, I wanted to share two things I've noticed about the karma system. These are ad-hoc observations, not rigorous empirical results, and while they might feel like ways to "cheat" the system, I hope by making them public and known, it serves to make the "market" for karma more efficient instead.
1. [Fairly confident] Posts appear on the front page unevenly throughout the week. As best I can tell there's a lull on Sunday and a spike on Monday/Tuesday. I'm not sure if this is due to unevenness in when people write, or unevenness in when mods promote posts to the front page. Regardless, since your post's karma depends in part on how long it remains on the front page (which provides more eyeballs), and that depends in part on what other posts it's competing against, there is opportunity here. Consider delaying publishing your post to a less busy time of the week.
2. [Less confident] Automatic cross-posting is a self-fulfilling karma signal. Having automatic cross-posting set up requires both sufficient author interest and sufficient moderator trust, since it's still a fairly manual process. This means that auto-x-posting is a fairly significant indicator of status/karma in the community, and such posts tend to do better in part as a self-fulfilling prophecy (of course they often do better because they're unusually good too - the karma system isn't broken, just slightly unbalanced). There's no way to replicate the automatic-x-post indicator in a manual post, but even just putting "[Cross-posted from MyBlog]" at the top of the text seems to provide a small boost.