Type of IP address that you want to use: IPv4 or IPv6
Number of potential systems on your network
Number of systems that are multihomed, or routers, which require multiple network interface cards (NICs), each with individual IP addresses
Whether to use private addresses on your network
Whether to have a DHCP server that manages pools of IP addresses
For an introduction to IP addresses, refer to available articles about the topic online such as the following resources:
To obtain IP addresses, register with any Internet Service Provider, or through IANA's Internet Registries. See IANA's IP Address Service page (http://www.iana.org/ipaddress/ip-addresses.htm).