The Four Agreements are:
1. Be Impeccable With Your Word.
2. Don't Take Anything Personally.
3. Don't Make Assumptions.
4. Always Do Your Best
I have read that the author has been influenced by Castenada, whose I have read nothing, but certainly there is a lot of PLN training programme and transactional analysis at the basis of his thought.
I have no idea whether the shaman’s theories have been adapted to nowadays world or viceversa.
Nonetheless, this little book (only 44 pages extremely easy to read) is a small pearl of wisdom which I would recommend to everyone.