Post interesting content but don't stop there. People's decision 2 vote is not solely dependent on content but also on d personality. Do favours 4 people (digg dia story) nd dey'll b more likely 2 resiprocate. But focus on serious (more consistent) diggers nd ur effort will more likely yield dividend. U can even go further nd form diggers gp outside of digg.
this works with twitter as well... if you retweet a bunch of peoples tweets you will get more retweets.. pretty obvious but it actually works.. i try to retweet my frequent followers often