Mealy Safety Device with 2 inputs
Without answering your assignment, I'd probably start by drawing a state machine.  This forces you to walk through the logic in a really visual way, until you really understand the question.

Once you have the state machine, you can write the truth table, and scan the truth table to find redundant states and get rid of them-- then maybe redraw the truth table.

There are a number of good sources on doing this -- https://www.youtube.com/watch?v=i0FK4fNTH9c for example.

Form there, you MIGHT be able to see your implementation, or you might not.  

If not, the formulaic way to flip flop implementation is to make a Karnaugh Map, reduce it to logic, and then implement the logic w/ flip flops.  I suggest poking around at 
http://www2.elo.utfsm.cl/~lsb/elo211/aplicaciones/katz/chapter6/chapter06.doc3.html

If your state machine is big, this can be quite a tedious exercise