When you reject, the most important thing to do is to START LOSING SPEED. Therefore, immediately, select idle thrust (reverse if you have it), and maximum braking.
To get the most out of the brakes, you need the weight of the aircraft to be supported by the wheels not the wing, so the appropriate action is to retract the flap. On a big aircraft, the spoilers will deploy automatically or will be deployed manually. This ensures that the weight is on the wheels.
Obviously, there is a danger on some types (eg Barons of some vintages) of confusing the flap control and gear lever - but then if you retract the gear, you will stop more rapidly - and before you all laugh at this, there is provision for deliberately retracting the gear on the ground in many large transport aircraft.
If you hit the hedge at 40 knots it will do a lot more damage to you and the aircraft than if you hit at 20, so give serious thought to all of this.
Needless to say, having cocked it up by mis-calculating your performance in the first place, you'll get to carry the can home with you.
[This message has been edited by Fokjok (edited 11 April 2000).]