The Glannon is quite good here. Study his questions carefully.

In addition, consider the following:

1.  Why is supplemental jurisdiction a good idea?

2.  Try to figure out a way of distinguishing between cases that (prior to supplemental jurisdiction) were called ancillary and those that were called pendent.

3. When considering supplemental jurisdiction, there are two questions to think about. First of all, what is the constitutional scope of supplemental jurisdiction? In other words, when is a cause of action that does not have federal subject matter jurisdiction on its own so closely related to a cause of action that does have federal subject matter jurisdiction on its own that they are part of the same constitutional "case or controversy"? The second questions concern the following issue: Even if supplemental jurisdiction is constitutionally allowable, is it statutorily allowable? Before section 1367 was enacted, to determine whether supplemental jurisdiction (then called either pendent or ancillary jurisdiction) was statutorily allowable, one had to look to the purposes of the statute that provided the main cause of action with federal subject matter jurisdiction. For example, if the main cause of action was allowable under 1332 (diversity), then one had to look to the purposes of 1332 to see if a court's exercising supplemental jurisdiction over a related cause of action would have been considered statutorily allowable. After 1367 was enacted, one only has to look to 1367 to determine whether it was statutorily allowable. 

4. In addition to answering the constitutional and statutory questions of whether supplemental jurisdiction is allowed, you need to answer the question of whether joinder is allowable under the joinder rules. If the Federal Rules of Civil Procedure do not allow the cause of action to be joined, then it won't help that the cause of action has supplemental jurisdiction.

5) Consider the following cases. Is joinder allowable? Is there jurisdiction for the joined action?