Do your background checks and know about what you goals are. Realise that propositioning bargaining is not going to get you far, the other person can potentially replace you easily using Internet so you need to be a nice person aiming for win win agreements. Know what the end you are looking for is
Don’t make concessions due to time pressure the other party is applying.
The good cop, bad cop strategy is an example of you being encouraged to take an inferior deal by framing it against something far worse. If dealing with this situation, ask to speak to the good cop alone and say you will walk away due to the bad cop’s behaviour unless things change.