Answer:
If either part of the compound subject can be used (correctly) as a subject by itself, then it will work in a compound subject as well.
Explanation:
Me and Frank thought it would be a good idea to review before the test.
Frank works, but does Me?
<em>Me</em><em> thought it would be a good idea to review before the test. </em>
No, it should be
<em><u>I </u></em><em>thought it would be a good idea to review before the test. </em>
And then we never put ourselves first in a compound subject, so the correct compound subject would be
<em>Frank and I</em><em> thought it would be a good idea to review before the test.</em>