Use your Inertia

When you want to achieve a speed, you have to burn fuel to get there. Why let that effort go to waste by braking to a complete stop when you could have planned ahead and slowly shed speed. The more momentum you have when you need to accelerate, the less fuel you'll need to use.

This goes hand in hand with not tailgating - you need to leave room to allow yourself to brake evenly rather than having to brake sharply and shed too much speed at once.