Kristen
I'm not sure this is the best way, but this morning on the quiz I
used the table from ch. 3 (sorry, I don't have my book with me now or I'd
reference the page number and all for you...) with pka's of different
molecules and ions to determine whether or not the leaving groups were
weak bases. Just having a good general idea of which kinds of molecules
are stronger or weaker bases will probably be pretty helpful, but when you
aren't sure for whatever reason, you can always refer back to that table.
-Leslie