What are some typical errors that a researcher should look for when reviewing journals?

Answer 1

I assume you are writing on Education Journals. I don't read them often anymore, mainly because of the research is often heuristic, without data analysis that is statistically tested, and usually, the research is not peer reviewed. In my opinion, much of it is not worth implementing because it was poorly tested. This is especially true in math and reading.

Answer 2

I'd look for experiments that haven't been duplicated elsewhere.

You'd also need to know statistics in order to determine whether the difference in two groups was significant.