1. An important one: Do not use an octane higher than that recommended by the car manufacturer. That Mobil Supreme doesn't help your Camry one bit! You're just wasting money! It's amazing how many millions of dollars are wasted every year because of this misconception.
2. You don't need to stay warm to avoid a cold. Cold viruses don't grow out of cold weather! In fact, staying indoors on a cold day INCREASES your chances of catching a cold because you're exposing yourself to more people who can transmit the virus to you.
3. You don't need to accept the pre-determined return policies of stores. You can negotiate your own if you're buying from someone with the authority to change the store's return policy. If they tell you that there's a "no return" policy. Tell then that you won't buy it unless they allow you to return the item unopened within 10-days. You can't do it at a chain where the employees have no authority to change the store's return policy, though.
4. You don't have to accept the terms of form contracts. Cross out the provisions of the contract that you don't like before signing it. If the other party accepts it, you just got ourselves a more favorable contract! But remember that they don't have to accept your modifications! This is harder if they want you to sign in front of them in person. It's easier with internet or phone orders where the terms of the contract come later in the mail with the item you purchased (E.g., a computer). Just cross out the terms you don't like, make a copy, and mail it back to them. If it's not that important of a provision, they may accept it!