Ask for a business card. This will help with your networking and memory for each company. You could also offer your own. Dressing neatly and appropriately. Smart or office casual is a safe bet.
Stillness creates an air of confidence and power.
Therefore, avoid fidgeting, touching your face too often, playing with you hair or using other distracting movements such as rocking. Listen to the details of what the company representative says and take appropriate turns - share the air space. Be articulate with specifics and sell yourself. Show confidence in your voice and body. An open and tall body posture will help communicate this.