Begin your search by asking friends who their photographer was, personal recommendations are always the best if you can get any.
Next step, search the internet, papers and also here on Hitched for photographers in your area, but you need no limit your search to local as many photographers can travel. With literally thousands in the country it seems daunting I know! So do start local.
Start by looking at styles and photographs that you like, can you see your wedding in those photographs and are they what you'd like as the end product? When you find photographs you like, make sure the photographer has an extensive portfolio either on or offline. As to see complete weddings if they don't have them online.
Narrow down your choices by price and style but don't let price dictate too much. Be aware of very cheap photographers, anything below £500 doesn't leave room for the photographer to have insurance or sufficient equipment with back up. Of course there are photographers who are just starting out that can afford to do weddings for cheap because they have another job to allow them to make a financial loss for the experience, if you find one of these make sure they can show a sufficient portfolio.
Whilst prices for photographers is like the length of a piece of string, a ball park figure between £800-£2000 for the "average" disc only package in the country. Prices can peek at around £8,000.
When you've collected some that you're interested in, ask to meet to see if you like them as a person. It's imperative that you get a long with your photographer, if you don't like them, don't be afraid to carry on looking. If you like them you will be happy on your wedding day = better photographs. When you meet, make sure they are very specific about what you get for your money, this should also be clear in the contract further down the line.
How do you tell if a photographer is good? Look for image sharpness, focus, colour balance, skin tone and good expressions as basic check boxes. If they have been published in magazines that's also a great sign of a good egg.
I hope that helps, I've tried to keep it short but if you want any more specific advise I'll be happy to answer!
Good luck :)