Is copying methods from a paper from the same group plagiarism?
Experimental and methodology sections are increasingly being recognized as "exceptions" from plagiarism, for reasons of practical necessity. For instance, I use the same basic technique to study different problems in engineering and material science. One of the sentences in my methodology section is:


  We use the SHAKE algorithm to constrain the bonds in water molecules [citation].


There are only so many ways to write this statement, and at the same time, I can't ignore this information, because it would imply a change in method. Is it plagiarism for me to reuse the same wording as in an earlier paper? If it is, I'm in big trouble. Similarly, if I were an experimental group, how many ways are there to say:


  We used chemical X from vendor Y as received.


For this reason—because often methodologies are very similar to previous methodologies within a research group–many journals now do not consider such so-called "self-plagiarism" of the methodology section to be a problem.