Talk to people who know the industry, people in similar positions and people within the organization before you go into your negotiations. Know what you can negotiate. You may be able to eventually persuade them to allow you job flexibility, but it's best to find the right fit with an employer during the negotiations, and leave only minor details for later. If your lifestyle, values, and priorities are not a good fit for that corporate culture, the job is not a good fit for you, and you are probably not a good match for them. Know that you are dealing with future coworkers.
Some people become adversarial and aggressive during job negotiations.
Some become soft and give in just to secure the job. Most people overlook that they most likely are negotiating with someone they will be involved with day to day. Therefore, honesty, forthrightness and politeness are crucial. On the flipside, you should pay attention to how you are treated during the negotiation phase of obtaining a new job. These are all just hints of how you will be treated later on.