I need tips on writing historically -ish. My instructor sent back my last essay with a few comments like avoiding indefinite articles and such. Are there any other guidelines I should follow.

Thanks for the help.

Avoiding indefinite articles? 0_o

I dunno about that one, but you should avoid personal pronouns, choppy sentences and use present historical tense whenever possible - those are the mistakes I most often notice in historical writing.

It's very good to hold your own personal rhythm while writing. For instance, my (natural) style of writing is to write a couple of longer sentences either explaining a point or detailing evidence; I then directly follow those couple of sentences with a short sentence "choppy" sentence that bluntly states what the evidence proves (relating to the paper's thesis).

dimmick is right when he says avoid choppy sentences, but if you are able to finesse them into the paper, be sure to do so. It stops the reader from being bored of listening to the author drone on and on in the same format.

What the teacher means by the indefinite article remark is that you should be specific. "An apple" just means some apple, somewhere. "Hitler's apple" is much more specific.

On a related note, my teacher makes a mantra out of the phrase "Don't be vague".