You can do as Electrode said and jam it all into one partition but it's generally accepted not to do this from a system security point of view. If you use seperate partitions it's easy to recover from catastophic failure and only replace what got broken instead of the entire system. Unless the machine your running is newer with a lot of memory, say more than 256M you should have a swap partition.
I generally setup my Linux boxes with "/", "/swap", "/usr", and "/var" partitions.