Other Work Experience and Voluntary work
There may be summer placements and employers that can be approached to offer visits and shadowing which will improve your knowledge of that field The Guide to Finding Work Experience document on the RHS highlights many ways to obtain work experience. There is also part time laboratory or other scientific work that can be done while studying. The Society of Biology lists a number of paid and unpaid summer placement schemes, possibly with the offer of expenses. Some examples are AstraZeneca, Cancer Research UK in their London Research Institute for students in their penultimate year, IAESTA a scheme backed by the British Council offers paid international work experience and The Wellcome Trust. The employment advisers and placement officer can give you more information on how to obtain these sort of opportunities.
Employers value skills that students gain in all forms of employment that are required in most jobs. These are skills such as communication, team working and organisational skills and should always be mentioned on a CV along with voluntary work experience. For local and national volunteering opportunities have a look at the volunteering section.
In areas such as teaching and medicine a certain amount of experience, paid or unpaid, is a requirement. There are some useful downloadable booklets eg on Health Care Scientist careers and medicine on the NHS Careers website. For information about what experience is usually needed in order to make a successful application for postgraduate teacher training, see the Get Into Teaching website. At the time of writing, there are special incentives for graduates who are interested in teaching chemistry.