At the bottom of this page is a practice test in music theory fundamentals. The questions are comparable to the ones you will find in the first part of the Theory Placement Test, but this practice test is longer and more comprehensive. It contains seven sections, each labeled by a Roman numeral.
Once you've taken the test, check your work against the answer key, which you can download below. To gauge how you did, count your mistakes; if you have fewer than 15 mistakes overall, you're likely to place into Theory I on the actual placement test. If you had more than 4 mistakes in any one section, though, you need to review that topic in more detail. (Count as a mistake anything wrong - one note wrong in a chord, one accidental missing in a key signature, etc.)
Should you need sources to help you review, there are many music theory fundamentals texts available. In our Basic Musicianship sequence, we use:
In addition, the first seven chapters of the textbook we use in our theory sequence provide a compact review:
The actual placement test also contains a section testing basic aural skills through melodic, rhythmic, and triadic dictation; a good way to practice for this section is to work with a friend who can play for you at a keyboard simple melodic fragments, basic rhythmic patterns in a given meter, and triads. Following this section, there are a number of exercises designed for students who have already studied music theory and ear training at the college level; successful performance on those exercises can lead to placement in later couses in the theory and aural comprehension sequences.
Good luck!