Can you do something for a local newspaper or your student newspaper?
You could also approach the PR department at your university, the people who send out newsletters and advertise the university.
As I understand it most jobs are around London which put me off, well working for journals like Nature etc.
I'm looking into medical writing now, see the EMWA website for info, and search for medical writing blogs.
I got advice about networking from my careers service. I've visited people that work in the area for information -"shadowing."
There is a website for the association of British Science writers with info too if its journalism you're more interested in. Follow technical writer links on the prospects website.