u have to esnure that u are following the directive term. a 25 marks essay will either be an evaluate, assess or discuss- it wont be a describe question. the thing about ancient history is that there are always differing views, different theories and different interpretations of the same evidence, and so the content is suited to an evaluate, discuss or assess directive term. a response should never amount to just story telling, and if u feel that u are falling into that trap, then use as much evidence as u can, both archaeological and secondary sources/opinions in your essays which will help u focus on the interpretation side of things.
however, be aware that sometimes directives wont be used. for example in last year's paper, i know that in the personalities section, one question asked "why agrippina was killed?" for 10 marks. in this case, u would just imagine it was an explain question.