I recommend that you read the following weblink from the Connexions Direct "Jobs4U" careers database. It is a bit of a heavy read, but it contains a lot of useful information. Pay particular attention to the "Skills & Personal Qualities" section, and the "Interests" section. Connexions has researched on what employers of firefighters are often looking out for in candidates who apply to them. If you have any of these qualities, get ready to talk about your qualities when applying for work. You will note from the article that employers of firefighters respect people who are concerned with the welfare of their local community. You could start demonstrating this now if you feel that you can help out at a local youth or community group (even if they aren't fighting fires).
http://www.connexions-direct.com/jobs4u/index.cfm?pid=62&catalogueContentID=633&render=detailedArticle
You can also visit your local Connexions Centre in England (a government service for young people) , or Careers Office in Wales and Scotland, for confidential advice individual to you. ... or ask at your school if a Connexions Adviser or Careers Adviser visits your school; if so you could book an appointment at school - it might get you out of class for an hour!
It is very competitive to get a job as a full-time firefighter, but there is a national shortage of "retained firefighters." A retained firefighter is basically someone who commits themselves to be within a short distance of a fire station, and be on call if needed. A person who proves themselves as a retained firefighter is likely to be ahead of the competition when full time jobs are advertised, because he has already been trained, and hopefully will have demonstrated his capability for the full time job. You did not mention whereabouts you are in the UK, but you can make direct enquiries to you local fire & rescue service. They should be in the phone book, or internet search on your "County" or your "Metropolitan Authority" and something like "Fire Service" or "Fire and Rescue Service."
Remember that other organisations have their own fire services. For example, The British Airports Authority (BAA) provides it's own fire service at British Airports.
http://www.baa.co.uk/
The Defence Fire Service, provides fire services to military and other defence sites. The RAF also employs firefighters.
Contact your nearest Army or RAF Recruitment Office to if you are interested in this. Remember, though, that service in any of the armed forces is quite a commitment, and you may serve a long way from home.
http://www.mod.uk/DefenceInternet/DefenceFor/Jobseekers
http://www.raf.mod.uk/
Non- BAA airports and some large private organisations have their own fire services. Your local Connexions Centre should have ideas about employers in your home area that may have their own firefighters.
Fire Magazine is an on-line magazine with articles covering all aspects of fire and rescue and the latest debates and developments. The "recruitment" link takes you to current vacancies. http://www.fire-magazine.com/
I hope this helps, but if you have a further query, please add it to your question. I shall check back over the the next couple of days.
... and finally a rhetorical question to you. What made you decide that you wanted to become a firefighter? ...and have you explored other options that you might well be suited for? Your Careers adviser can offer you a "gentle and painless" interrogation about your general interests, abilities, likes and dislikes, and then come up with a range of career suggestions. I don't want to put you off firefighting, but there may be alternatives that haven't even crossed your mind yet. A chat with a careers adviser might reveal a few surprises.
EDIT 30th Jan 2008:
Relevant links to M.Keynes area:
Buckinghamshire Fire & Rescue Service: http://www.bucksfire.gov.uk/bucksfire/default.htm
Careers information: Buckinghamshire Fire & Rescue Service http://www.bucksfire.gov.uk/BucksFire/Recruitment/
Bedfordshire fire service:http://www.bedsfire.com/
http://www.bedsfire.com/recruitment/recruitment.htm
Re: “..employers of firefighters respect people who are concerned with the welfare of their local community.”
Possible lead for a voluntary opportunity (when you're age 16) to demonstrate concern to the community ... “safety tour guide “ in Hazard Alley, Milton Keynes. Training is provided.
http://www.safetycentre.co.uk/volunteers.html
Connexions, Lloyds Court, 662 North Row, Milton Keynes, MK9 3AP Tel: 080 800 13219 & 01908 232808 http://www.connexionsmk.co.uk/RunScript.asp?p=ASP\Pg0.asp
Connexions opening hours: Mon, Tues, Thurs 9am-5pm, Wed 10am-6pm Fri 9am-4:30pm
email: miltonkeynes.connexions@vtplc.com
Details of Public Services courses (relevance to Firefighting and other public service) at Milton Keynes College can be found on page 5 on the following document:
http://www.mkcollege.ac.uk/docs/Support%20-%20Marketing/FT%20Prospectus%2007_08/sports.pdf