By history, I assume you mean 'history on the page' by historians, rather than 'history as it actually happened' to people in the flow of time.
Does the historian open his text with a detailed survey of what has been previously written on the topic? Does he interrogate these source for mistakes; for being factually out-of-date; being superficial; for blithely parroting 'what others have said' without checking them?
Does the source cite good references for each claim being made? Are these references directly available to the reader as open footnotes on the page, or are they being hidden away as endnotes? How fulsome are these footnotes? Are there little comments after a reference, which show the work has actually been consulted and examined, such as: "This book has been somewhat superseded by Boffin (1987) on the matter of X, but the book remains reliable when discussing the topics of Y and Z."
Are these references generally reliable (i.e. are from good publishers or independent scholars or non-predatory journals?)
Has the writer taken his sources at face-value, or has he consistently asked questions of them such as: has this older fact been superseded by new data; did author X have a blind-spot; did author Y do good work but overlook a key source?
Is the text on the well-known 'pressure-points' of history, meaning those points where the study of history 'goes off the rails' and into 'fringe' topics (e.g. a claim that 'Shakespeare did not actually write his plays', or that 'there was once an Arthurian land spur between Cornwall and the Scilly Isles', would automatically ring alarm bells...)
Is the author explaining his reasoning in the text, and is this reasoning subtle rather than about 'us and them'. e.g.: "It is commonly assumed that fact X relates to fact Y, and this was the case until the new discoveries of 1956. I will now explore ways in which the rush to the new paradigm in the late 1950s may have overlooked a few valuable aspects of the earlier consensus...". Or does he just jump in and say: "All that post-1956 stuff is mumbo-jumbo, and the Victorian era got it ALL right!".
Does the author have an 'academia bias', meaning that they parrot the superficial parrotings of other academics, without checking the facts back to their original source?
Are the references they give generally available, or are they very difficult to obtain - such as obscure small-press editions, long out-of-print and unobtainable items, ancient theses which have apparently never been digitised and placed online, etc?
General reputation of the author and place of publication, although one should always try to make one's own judgement by actually reading some of the work. There are many grumpy / superficial reviewers out there, and reviews should not always be taken as an accurate yardstick of quality.
Ask yourself 'what might be the reason for falsification?' Is there a political, national, or personal angle here, that should make one wary? Why might someone want to confabulate a fake history on this topic?
What exactly do you mean by this? Do you mean how do we know what historians are telling us is true or how do we know that all of the artifacts and documents we use are reliable?