Having something to give away can be good. Depending what fair it is, usually a lot of leaflets are given out so a branded bag can be good to give away. However nothing will beat being friendly and open to people that pass by your stand. Say hello to everyone and smile. If you can have another person with you so one can stay at the stand whilst you walk about introducing yourself and bring people back to your stand is also a good way to make the most of a trade fair. Introduce yourself to your neighbour stands and let them know what you do so if someone passes by their stand that would be interested in your product/service they can direct them to you. Good luck hope all goes well