There are three main ways of finding a translation service. The first port of call should be your local directory such as the Yellow Pages. If you have a specific business directory for your area then even better. Simply look up "translation" or it may sometimes be under "translators & interpreters". Have thumb through the listings and earmark some to contact.
The second, and easiest, means of finding a translation service is through the internet. Using the main search engines such as Google, Yahoo! and MSN can bring up hundreds of listings. One added advantage of using a search engine is that you can be more specific with your searches. For example, if you are looking for a translation service local to you type "translation service London" or "translation service Oxford". Similarly if you are in need of a specific language try something like "German translation service".
With search engine results you will be presented with two types of listings, paid listings (advertisements) and organic listings (non-advertised results). It is good to bear in mind that those with organic listings are there for a reason, i.e. the search engine naturally sees them as important sites for translation services. On the other hand paid listings will be from companies that need the business. This is not necessarily a negative thing but good to consider when making a choice.
The last means of finding a translation service is to ask colleagues, friends or family. A personal recommendation is always best.