The first thing you should do before overtaking is:

• A. Increase your speed.
• B. Sound your horn.
• C. Make sure it is safe and the way is clear of oncoming traffic.
  Explanation:

  "You will need to make sure you have enough room to overtake, which is a function of the ability of your vehicle to get to the speed limit quickly, and how long it will take to pass the vehicle while doing the speed limit. You also need to check for solid lines on the road that mean no overtaking, and whether another vehicle has started to overtake you"