"Careers fairs" (also known as jobs fairs or recruitment fairs) are a useful resource for candidates to use to find out about potential employers. If you attend a fair, you will be able to talk to HR teams and current graduate trainees from many companies, all in one location. You will be able to find out about specific details such as employer's application requirements and interview tips.
Talking to firm's HR staff at careers fairs is useful because these people will let you know important details such as the best time to apply for their graduate jobs and what to watch out for on your application form. Current graduates offer you a different perspective; ask them about the working culture at the firm and what day to day work entails.
It is important to act professionally and demonstrate your employability at careers fairs. Be careful what you say and who you talk to; many HR employees are also interviewers and the people who accept or reject application forms. Always be polite, HR will remember you if you do decide to apply to their firm!
Network as much as you can at careers fairs and ask for business cards wherever possible. Many company employees are more than happy to give you their personal information and may even suggest contacting them with any further questions in the future, if you decide to apply to their firm.
For further information on careers fairs: Human Resources (HR), General Interview Advice.