You know, I have a theory on Bejeweled that your computer speed can affect your score. Some nights, I play game after game and can't get blazing speed. Other times, I play game after game and every game is over 200,000. If I'm getting low scores, I'll clean out my history, restart my computer and do whatever I can to pick up computer speed.
In addition, what everyone has said, although we're all using different boosts, which I find interesting. I use the last 3. The most important thing is to get score multipliers. You can do blazing speed all you want, but there's a huge difference between blazing speed at X2 and blazing speed at X5. When I play, I focus on multipliers.