Assuming you're enrolled at Excelsior College, use the "MyAccess!" site via your "My Excelsior College" page. There are plenty of practice essay topics there, and good tools for evaluating your writing. Also, make sure you know one of the three citation styles down cold -- there are no reference materials available when you take the exam. (This annoyed me a little, because Excelsior's Information Literacy course stresses that you should always refer to a style guide, and not try to memorize citation styles, but the English Composition exam contradicts that.)

Practice the "five-paragraph essay" format that you'll see discussed on lots of web sites and forums. This is especially appropriate for the argumentation essay. You choose three arguments that support your side of the issue, and write a paragraph for each of them. Then you write an introductory paragraph that has a thesis statement and lists your three arguments. Finally, you write a conclusion paragraph that summarizes and re-states (without being redundant, of course! ) your argument. Like they say in the military, "tell 'em what you're gonna tell 'em, tell 'em, then tell 'em what you told 'em."

-Gary-