How do you set up laptops that are used on and off site?

This is something that we are trying to create a standard practise for. I work on the service desk as opposed to onsite doing installs but I am still curious as to how this should be done. Obviously my first thought its cached credentials. However there are other issues such as proxy's e.g. on site group policy defines a proxy however when the user takes the laptop home this won't work. Could a PAC file be pointed to so when the user is at home it would fall back to no proxy? Another thought is using network locations but I'm not sure how this is controlled by group policy. Other issues are stuff like folder re-direction and offline files. I would like to know if anyone has got a way to make use on and offsite as seamless as possible.