It's hard to pin down any specific actions that you should never do, because morality is very much a situational thing. Consider morality not as a book, with all the commands set down and unchanging, but more as a computer program, where a different input (human situation) can result in a different output (human action) even though the same process is being run. As a result, the only things you can say that you must never do are blanket statements such as 'rights must be recognized except in lesser of two evils situations', not specific statements like 'never steal your little brother's sandwich'.
That said, I myself have still not figured out precisely how morality works. I have some interesting ideas for rules, though, such as:
- Rights must be recognized unless you are in a lesser of two evils situation (this is the statement I mentioned above).
- The importance of a being's rights is based on its ability to care and to desire things.
- In situations where you are not being affected, the correct course of action is always that which maximizes happiness with the minimum amount of infringement on rights.
- In situations where you are being affected, it is okay for you to maximize your own happiness so long as it is either a lesser of two evils situation or you are not infringing on any rights.