How do I get the Score Addict achievement in Angry Birds?

I recently finished getting three stars in all stages across all three worlds of Episode 1 in Angry Birds. I have approximately 3 800 000 points. I need 4 000 000 points to get the Episode 1 - Score Addict achievment. (Or maybe I need an intervention?) There are 63 stages, which means I need to score an average of 3,000 more points per stage to get this achievment.

This doesn't seem possible.

Are there things I can do to get higher scores besides smashing more blocks? Multipliers? Smashing certain items?

There are a number of stages where you can exceed the three stars score by a healthy margin. Most of the time, if you used all of your available birds and still got three stars, you can improve your score by completing the level with fewer birds. Obviously, it's going to be difficult to improve some of your scores, but even adding 10 or 20 points to some of the levels will help.