The main advice I would give is to try to find out which bit of science you enjoy most – there are sooooo many different types of scientist – from molecular biologists to astronomers and particle physicists. If you get good GCSE science grades and maths and science A-levels there is a whole world of opportunity out there!
The best advice I can give is to work hard at school and get good grades, then go to the best university you can, and work hard there too (but you are allowed to spend some time having fun as well, life isn’t just about work!).
And only continue with science if you enjoy it!
I would advise them to develop an interest in science outside of the classroom – perhaps by reading up on their favourite topics, or joining a science club. Perhaps start reading popular science magazines like New Scientist, and listen to podcasts like:
I’d say that you should start to get curious about the world around you, questioning things that people tell you, particularly if they have no evidence to back up their claims (within reason – I don’t mean question when people tell you not to jump into molten lead etc.). Healthy scepticism (which means doubting claims until they are backed up with evidence), balanced with an open mind are the starting points for a scientist.
Also, I would advise getting some work experience. Get in touch with a local university research department, if indeed research is what you’re interested in, who research something you find interesting. For example, in the Institute of Cancer Research, where I work, we regularly offer school students work experience. You will, hopefully, find that most departments are happy to have you spend some time observing or helping out with research – because you might be a future PhD student!
I would definitely recommend doing a PhD. It’s tough, but it’s the best experience to teach you a scientific way of thinking (problem-solving, dealing with frustration from exp not working…) that is essential in a science career.