Suppose I want to draw a NFA that doesn't accept a language containing $aba$. Would this work:
NFA that doesn't accept a language
automata
Construct the obvious four-state NFA with minimum number of transitions, which DOES accept 'aba' (and no other string).  Complete it as a DFA by adding a 'dead' state, then adding all missing transitions from the other states to the dead state, plus two transitions from the dead state - one on 'a' back to the second NFA state, one on 'b' back to the third NFA state.  Now invert the finality - i.e change each final state to non-final and each non-final state to final.  You now have an NFA (DFA, actually) which accepts all strings not containing 'aba'.