Exhibits take a lot of work to coordinate and set up. The larger the conference, the easier it will be to convince vendors to participate. Smaller conferences may not even want to have exhibits. If you do have an exhibit, assign a committee member to be in charge rather than taking this on yourself.
An exhibit hall must be easily accessible and must have adequate space to accommodate vendor booths. There may be costs associated with such a hall. Some facilities require that their own people set things up. Make sure you know what is included with any rental costs, and what you may have to pay extra for.
Make sure that there is adequate time for attendees to visit the exhibits and to talk with vendors. Also, consider including vendor-sponsored sessions at the conference, or having the vendors participate in panels. Depending on the benefits to the vendors, you may ask that they pay for exhibit space, or leverage their participation by asking them to sponsor one or more conference activities (reception, meal, etc.), or to provide conference bags.