Basically the two main types of distros are Debian and RHEL/Centos based.  I'm just going to give a quick overview of how the configuration of IP interfaces works in Debian/Centos based distros.

*Just one thing to remember, when setting IPs statically you have to manually specify a DNS server in /etc/resolv.conf (since DHCP is what normally does it automatically)

Debian/Ubuntu/Kubuntu/MEPIS

The IP (DHCP & Static) configuration is done from the following file: /etc/network/interfaces

Here is how the default DHCP configuration looks:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
auto eth0
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

Here is an example of setting it statically:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
auto eth0
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet static
        address 192.168.1.147
        netmask 255.255.255.0
        gateway 192.168.1.1

*Just one thing to remember, when setting IPs statically you have to manually specify a DNS server in /etc/resolv.conf (since DHCP is what normally does it automatically)

Centos/RHEL/Fedora/Mandriva

The IP (DHCP & Static) configuration is done from the following file : /etc/sysconfig/network-scripts/ifcfg-eth0

*Note the "eth0" at the end, each device has it's own entry within the network-scripts directory.

Here is how the default DHCP configuration looks:

# Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller
DEVICE=eth0
BOOTPROTO=dhcp
HWADDR=5A:G1:29:4A:1C:76
ONBOOT=yes

Here is an example of setting it statically:

DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.1.245
GATEWAY=192.168.1.1
NETMASK=255.255.255.0
ONBOOT=YES

*Just one thing to remember, when setting IPs statically you have to manually specify a DNS server in /etc/resolv.conf (since DHCP is what normally does it automatically)