1. Calibrate your battery
2. Adjust your settings
3. Buy the Right Processor
4. Only run programs you need
5. Dim your screen
6. Disable unnecessary programs
7. Keep operating temps down
8. Don't watch DVDs or play games
9. Limit external devices
10. Don't standby, hibernate
11. Clean battery contacts
12. Use the battery
13. Don't leave it in sunlight
14. Turn off wireless and Bluetooth
15. Decrease hard drive activity
16. Avoid using the CD/DVD player
17. Be picky with software
18. Less is more
19. Turn off speakers
20. Carry a spare device or battery

Source: 20-tips-to-get-more-juice-from-your-laptop-battery