Character sketches should focus on the character's motivations and descriptions of the character's traits, as well as how they affect the outcome of the play. It’s also a good idea to choose quotes from and about each character to develop and support the analysis.
In addition to your interpretation in the context of the play, why not also compare the characters of Caesar, Brutus, Cassius, and Antony to modern political figures who also would be "honorable men." (Like the characters in Julius Caesar they wish to portray themselves as such, do they not?)
There seem to be good parallels available to you.
I can give you some pointers and some scenes to look at, but character sketches really depend on how you interpret each individual character and his/her actions. A key question in "Julius Caesar" is whether the characters' actions are morally justifiable.
Caesar: physically frail, extremely arrogant, but kindly - and, in Shakespeare's play (though not in history), doesn't really do anything wrong.
Brutus: called "the noblest Roman of them all" by Mark Antony at the end of the play, and praised in high terms by Cassius. Yet every major tactical decision he makes in the play is wrong: look at the way his soliloquy in 2.1 goes backward, beginning with a conclusion ("it must be by his death") and then working to justify it. His wife dies of grief at his absence, and he seems to be drawn into the assassination largely by Cassius' manipulation of his own self-opinion and arrogance.
Cassius: the architect of the conspiracy. Caesar doesn't like him or trust him (see 1.2) but then, where Brutus is wrong, Cassius is right (his battle plans, and his suggestion to kill Antony might - if heeded - have both averted their defeat at Philippi).
Antony: Caesar's favourite, and a lover of acting and of theatre, Caesar tells us. But when is he acting? Do we believe his speech over Caesar's body, or his funeral oration? How does he know, in 3.2, where Brutus and Cassius' daggers ran through Caesar's robe - he wasn't there! Loyal - or suspicious.
Check out the links below for some more help. The second link below is great!
If you're researching this online, make sure your looking up the Shakespearian characters, as Shakespeare took some liberties with his story.
In simple terms:
Caesar: Though physically weak, he is an arrogant ruler who thinks highly of himself. He will do what he can to win the approval of the people.
Brutus: A thoughtful, stoic man who wants to do what is right for the people of Rome. He is from a historically important family and his name carries a lot of weight in Rome. He is easily swayed by logical arguments and, at times, flattery.
Cassius: A manipulator who doesn't like to see others have more power than him. Cassius is the one who initiates the plot against Caesar and knows he needs Brutus' help. Cassius sided with Pompey, and still isn't fond of Caesar.
Antony: Antony is a plebian who has risen through the ranks and is thought highly of by Caesar. Antony is often considered Caesar's right hand man, and is also manipulative as well, using his words and playing on logic and emotion to his benefit. He can also be arrogant when he wishes to be.
1. His loyalty to Caesar:At the feast of Lupercal,we see his great respect and loyalty to Caesar when he says 'when Caesar asks anybody to do something it should be taken as done'.
2. A lover of sport :Antony is going to run a race at the feast of Lupercal-he is not weighed down by the politics, intrigue and schemes of the others in the Roman Senate.He is spoken of by Caesar as a man who 'revels long o' nights' and later by Cassius as a 'masker and reveller.
3. The shrewd orator:When Caesar is killed, Antony runs away, for he knows his physical safety is more important at that point of time. Later he carefully approaches the conspirators, choosing his words carefully.His speech and its result show how cleverly he plots the downfall of the conspirators.He appeals to the sentiments of the people , mentions the gift of Caesar to each one of them and carefully builds his case against the conspirators disproving them from point to point and all the while suggesting what they should do.
3. The unscrupulous member of the Triumvirate: Antony shows himself for what he is-an oppurtunist when he suggests to Octavius that Lepidus should'nt be given an equal share in rule of Rome.
4. The Merits of Antony: In addition to being a shrewd orator and a good general, we also see an honest side in him which has genuine respect for Brutus in the end when he says that he was an honourable man.