Most use TCP/IP. Serious LAN Parties have IP's either dynamically assigned (DHCP) or you are given an IP upon registration.
<< Since yesterday, it was a whole mix up and we sat there playing one game and the others, another cause we >>
Someone needs to get on the ball and set PC requirements, Network settings, game settings, etc. Some sort of organization heirarchy ( a manager, boss, owner, ect.) and set ground rules for established game playing because without a standard you could have a Cisco switch with 100Mbit full duplex ethernet but you will be all dressed up with no one to frag.