The Universal Declaration of Human Rights, and Sustainable Development
First a couple of definitions:
Morals, are the rules, the Do's and Don'ts that you gauge your actions against when deciding "Should I do this or not?". Morals are laws, commandments, that long mass of text that you scroll past when creating a game account and click "I agree" to without even reading, but that actually contains a code of conduct that you must obey if you wish to play the game.
Ethics are the rules and principles by which you create your morals. If morals are the laws, the ethics are the constitution of that law. For example: if one moral is "Thou shalt do no murder", the corresponding ethic that produced that moral is "Human life is valuable and should never be needlessly extinguished".
So to lead an ethical life, you need to pick some ethics and create your morals from those ethics.
Now comes the problem: which ethics should you pick? Which are the good ethics? Is there any consensus on what are good ethics?
As it happens... yes, we as humanity have actually come together and decided on a starting-set of good ethics. That collection of ethics is called...
We have, as a world community, come together to declare that the UDHR is essential for both individuals and the world society as a whole; we consider the UDHR to be beneficial to all humanity, both for the one person and for the collective of persons.
But the UDHR is not fully implemented in all parts of the world, and it is being violated — to smaller or more extensive degrees — in all nations.
Therefore: working to implement and safeguard the UDHR is to work for humanity's best.
Can you guarantee that the result is for the best? No, you cannot. No-one can guarantee that. But by adopting the ethical principles of the UDHR, you have at least set your intention to work for something that the world community as a whole is beneficial for the human and the humanity.
As a bonus, you may want to adopt the principles of Sustainable Development. Sustainable Development was defined in the report by the Brundtland Commission, presented to the United Nations in 1987.
Sustainable Development is defined as:
Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. It contains within it two key concepts:
The concept of 'needs', in particular, the essential needs of the world's poor, to which overriding priority should be given; and
The idea of limitations imposed by the state of technology and social organization on the environment's ability to meet present and future needs.