If you have a game in your DS, and you want to go to the DS menu, hold down start button until you see the Nintendo DS logo. Then when you touch the screen the menu should appear!
NOTE: You will have to do this every time you turn on your DS.
If your playing a game and your battery is low then press select and press the down on the volume key to toggle the brightness. You can also do this on the dsi menu, dsi shop etc.
When you turn on the DS it will make a noise, however on your birthday it will make a differrent noise.