The most ethical way to avoid charges of plagiarism is to a) carefully reword passages one would like to use b) cite the sources that are well know c) only plagiarize sources no one else will find d) cite all sources whenever possible

The most ethical way to avoid charges of plagiarism is to cite all sources whenever possible. Plagiarism is whenever one uses others' words and ideas and doesn't cite them, therefore giving the message that they are one's self. The best way to avoid it is by giving credit to the person that came up with that idea, and the way to do that is by citing. It doesn't matter if the source is not well-known because you are still giving credit. However, most times for academic papers one is required to only use credible sources. In such cases, one should not be taking ideas from unknown sources.