Editing Wikipedia, especially articles on controversial topics—gives you good practice on extracting useful information from biased sources, and also gives you a better idea of how much you can trust information on Wikipedia (or any other source whose truth-filtering-mechanism isn’t better than Wikipedia’s). The history of distant countries or religions is a good start, because you’re less likely to start already attached to a particular interpretation but the sources you meet will still be mostly biased.
Editing Wikipedia, especially articles on controversial topics—gives you good practice on extracting useful information from biased sources, and also gives you a better idea of how much you can trust information on Wikipedia (or any other source whose truth-filtering-mechanism isn’t better than Wikipedia’s). The history of distant countries or religions is a good start, because you’re less likely to start already attached to a particular interpretation but the sources you meet will still be mostly biased.