3 – You are advised not to try to change both shifters at the same time as you risk derailing the chain or getting it stuck, or even breaking it.
4 – Unless you are sure of yourself, and are deeply worried about your pace, avoid changing several gears in one go.
5 – Avoid crossing your chain.
6 – As much as possible, try to anticipate your gear changes based on what you see coming up ahead. For example, don’t wait until you’re in trouble on a very steep climb to switch to an easier gear, because you’ll have a hard time with the switch due to the amount of force that you’re having to exert on the pedals.