When you think Evidence, you think hearsay. Yes, hearsay will be tested on the MBE, but it won't be the only topic. In other words, knowing hearsay and the hearsay exceptions alone will not be enough. Be sure to understand impeachment and character evidence. Some specific issues to look out for:
Character evidence vs. impeachment
It is important to know the purposes for which evidence is being offered so that you understand whether you're dealing with character evidence offered substantively or for impeachment purposes. The MBE really likes questions that exploit this distinction. For example, some evidence questions will ask whether a given item of evidence may be considered substantively, for impeachment or credibility only, or for both purposes.
Evidence admissible at sentencing
This is one of those things you wouldn't expect to see tested, partly because it's not taught in most Evidence or Crim classes. But we've seen a couple of questions concerning the admissibility of evidence at the sentencing phase of a criminal trial. State rules vary, but under the Federal Rules of Evidence, the only rules applicable at sentencing are rules of privilege (which are technically not federal rules of evidence in the first place). Remember that, generally speaking, anything may be considered at sentencing unless it implicates a testimonial privilege.
Co-defendant statements & the Confrontation Clause
This also arises as a Crim issue, but often comes up in Evidence. Since the mid-1990's, the Confrontation Clause has been an evolving area of law, but as it becomes more settled, it's likely to appear more often. So make sure you get this down. Co-conspirator statements, a related but separate issue, have also appeared recently.
Best evidence rule
It seems like the best evidence rule comes up often as an answer choice, but not necessarily a correct answer choice. Learn the best evidence rule (see Evidence – card 26), but remember that it only applies if evidence is offered to prove the contents of a writing – not just if the evidence includes a writing.