Keep your idea secret until a patent application has been filed, but before you start that process check that your idea is really new, otherwise it won't be granted a patent. Check product lists from manufacturers of related products, specialist publications, shops, catalogues. Check it's not already been patented, either yourself (at a patent library) or though a patent agent or search bureau (cost about £650-700).

I've checked and it's not - but how can I be sure people will want it?
Check there really is a market for it: who wants it? Where are they? Will it solve an existing problem better than anything else currently available? Look at which companies and products are your potential rivals and what market share they have - can your invention compete with what they offer at a competitive price?

It passes those tests. What next?
Write down clearly what your invention is, how it works, how it could be made in bulk and at what cost, and what its advantages are, including a simple drawing if it's mechanical or electrical. Then take out a patent either yourself (very difficult) or via a patent agent.

What does getting a patent cost and how long does it take?
If you do it yourself, Patent Office fees will cost £200 from initial filing to patent being granted, which takes about 33 months (its fast track system can take under a year for the same price). But drawing up patent documents is a skilled job so it's usually better to use a patent agent - the Chartered Institute of Patent Agents can put you in touch with one. For a simple invention they may charge £600-£1,000. Your initial application protects your invention for a year, and although protection can be extended it becomes more expensive, especially for international patents. Try to find a company to buy or license your invention in the first year to save money.

How do I market it?
Once your invention has been patented, you can set up your own firm to make and market it, approach other firms to sell it, or license it to them. But don't talk to them unless they sign a confidentiality agreement (usually drawn up by a specialist solicitor) first, so they don't steal or reveal your idea. For the best chance of success make a prototype and stage a smart presentation.

If they say yes what do I do next?
If they want to buy your idea or license it from you, you both sign an agreement. This usually gives you an upfront fee - often quite small, such as £500-£5,000 - and a royalty on sales, usually 2-7% of the selling or manufacturing price of the invention. Consult a patent agent about what is fair.

Can someone else market it for me?
Yes. There are technology brokers who do this, but beware: as well as reputable ones there are rogues preying on new inventors who offer an initial marketing assessment of your idea. The assessment may be generalised waffle recommending that you pay them £3,000 - 4,000 to market your invention and saying they will match your investment, but after you pay them, they don't live up to their promises. Check a broker's credentials: ask for names of satisfied clients and talk to them. If the broker won't supply any names, avoid the company, or get a recommendation for a broker from the Patent Office.

What about marketing it at exhibitions?
Inventions fairs and exhibitions typically charge about £400 for your own stand. You may meet interested companies, get tips from more experienced inventors, garner some publicity or even win a prize for your invention.

Is there any government help for inventors?
Yes. The Department of Trade and Industry's Smart Awards help individuals and small - medium sized businesses research and develop new products and processes that are a significant technological advance. For feasibility studies it covers up to 75% of the cost of the project; for development to prototype it covers up to a third of the cost up to £130,000. Apply through your local Business Link office.

Where can I find out more?
The Patent Office: 01633 814 000.

Institute of Patentees & Inventors : non-profit association offering information, meetings, contacts, guidelines, booklists: 0172 434 1818.

BBC Tomorrow's World International Inventions Fair: 01202 762 252.

Free samples of documents such as confidentiality, licencing and secrecy agreements from Malcolm Cook on 0800 026 7889.

Chartered Institute of Patent Agents: 0171 405 9450.