What steps should be taken in a molecular lab environment to help ensure that DNA samples/stocks are not contaminated, or contaminate other objects in the lab?
From the comment section:
Mostly segregation of PCR-amplified DNA from non-amplified DNA. Typically no DNA or sample should ever enter a specific room designed to prepare the MasterMix for PCR (this is true for diagnostic labs, in the research one I never saw that). For the rest, following good laboratory practices (google that) should be enough.