My acceptance of some scientific theories is based on my assumption that most researchers are, at least, not likely to lie about their results. I also hope that not a few act with consideration of the ethics of reporting research. Then, it seems unlikely, from my perspective, that so many scientists would not agree on something if it weren't independently observable, testable, verifiable. I also assume that those people who make up the majority of their fields are actual scientists when I accept a theory.
I must emphasize, however, that like in the classic quote where Sherlock Holmes declares that he couldn't care less if the earth revolved around the sun, many of the theories I encounter can be true or false and it wouldn't have any bearing on my day-to-day. In particular, if evolution isn't the explanation for the diversity of earth life, it doesn't hurt me now to assume that it is the explanation, and I know that taking evolution as a base permits some useful science to be done. Other theories, because they are theories, can be tested by me with the appropriate equipment to either confirm or disconfirm the theory with sufficient rigor to satisfy my own sense of what is true about the world. That is what separates the acceptance of a theory from belief. Beliefs are those assumptions which cannot be tested, but a theory offers a means, even if that offer is never taken advantage of, to base your assumptions on ones that are more sure.
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