It seems that everybody here has covered it quite well
anyway, im doing Augustus and the Julio Claudians and i find it great!
Yeah as other ppl have probably said know the ancient sources,
know the problems associated with these ancient sources
(i.e. Tacitus's obvious bias against Tiberius and against the prinicpate in general
Suetonius's focus on character not details etc)
then learn the modern historians - partularly their views of certain events
(e.g. Mommsen's view of the dyarchical nature of the prinicpate)
one last thing: Have your own view! You will most likely be asked to
assess or evaluate the achievements of the emperors
one thing to consider is that even though most of the emperor's are generally viewed as bad you have to consider that the empire did not collapse because of it - its impact was only on the higher echelons of Roman society.
During the time of the Julio-Claudians the empire was managed quite well