Just in case you hadn't worked these out yet:
1. You likely have 'Flash Headlights' mapped to the same stick you are steering with. When you click the stick it flashes your lights. Lots of pad users drive around accidentally flashing their lights and I can tell you it's quite annoying

So either work out a way of not clicking the stick while steering or map flashing headlights to a different button.
2. Some cars have DRS and/or KERS. The overtake button activates these (hold the button down). I don't have a full list to hand but the Super Formula is a good example. If you are in a car that has KERS you will see an extra battery icon next to the fuel gauge that depletes when holding down the button.
Enjoy!