1. Dress professionally! Really professionally! Just because a track suit has the word "suit" in the name does not mean that it is a good wardrobe choice. Leave your shower shoes at home. I am saying this because last week, these were actually issues at the job fair where I spoke.
Do not dress for the entry level position for which you are applying. Dress for the job you would like to eventually grow into. If you want to be the manager in 5 years, look as though you would present well to clients and subordinates. Please be aware that the tattoo on your neck or the piercing in your cheek many not be appealing at a certain level of job. I am not against either, but there is a time and a place, and your job search should target your most professional persona.
2. Smile! The easiest way for me to pick the career unemployed people out at the job fair is because they look like they showed up at gunpoint. I know that you may be thinking: "Another job fair and very little prospect. Great! I got dressed up because my unemployment counselor told me to, and no one is that interested..." No one is that interested because you are not interesting. You are feeling sorry for yourself!
Put your best foot forward in every interaction. There are a handful of people there who are engaging every recruiter at the job fair. They are being personable and likeable. People hire who they like!!!
Even if the people who are hiring are not in your field, have a brief conversation. Give them a resume and personal business card. Set yourself apart. Ask for referrals. Network with the professionals who are there. They may know someone who can assist you.
3. Be confident! A firm (not bone crushing and not a limp fish) handshake, good eye contact, and strong posture will go a long way. Fake it 'til you make it. Come off as professional and people will want to have you on their team.
In short, be engaging, prepared, professionally dressed, and cheerful. Be the person you would want to work with. Be the person you would eventually want to work for. When you present as a successful professional, people believe you. And the money comes rolling in!