Looking at the Travel Assignment, I approached most people face-to-face, which is obviously the best method. I would rather do this as it is more personal, people can see who they are talking to and I think you can build up a rapport. Marie Curie nurse, Sue Irwin, was the only person I didn't approach in person.
Obviously it may be difficult to do this all the time, but I think I will 'mix it up' - emailing, phoning and visiting workplaces.
I have decided that if a place is open to the public, I will call in, if it is an office, I will phone or email.