The government, as well as other non-government sponsors, hold conferences to help you in your quest. Procurement conferences are a good way to meet and speak with government buyers and large prime contractors. Some areas of the country have several conferences per year; other parts have only a few.
Usually you won't get a contract at one, but you can make valuable contacts. The "FedBizOpps News" area of the BidNet site will often announce these events and tell you whom to contact. Other government web sites post these conferences on their calendars as well. You also can learn about upcoming conferences and events from your local PTAC.