Using static or dynamic IPs depends on your application.
There are a few considerations when connecting a broadband link to your computer or network.
Connecting a single computer
Usually, the package your ISP sends you prior to your due date has everything you need (except a Network Interface Card or NIC) to connect a single computer to the Internet. If you follow the instructions in the box, your connection should come without a problem.
Connecting multiple computers
In order to run more than one computer on a single broadband connection, the computers must be networked. A computer network, or Local Area Network (LAN) requires specific hardware, such as a Network Interface Card (NIC) for each computer and a device for connecting all the computers together, such as a hub, switch or router (sometimes called a broadband router).
Each computer on the LAN can be configured with either a static IP or dynamic IP. The configuration you use will depend on your application. If, for example, each computer on the network needs to be “visible” on the Internet so that other computers on the Internet outside your network can connect to them, you should use static IPs. (Most ISP connections come with dynamic IPs. You can usually purchase static IPs from your ISP for a small monthly fee. Another reason to use static IPs is to run servers that are accessed from the Internet, such as Web and email servers. With a static IP configuration, you should use a hub or switch.
With a dynamic IP configuration, each computer on the network runs on a private, or non-routable, IP unaccessible from the outside world. With type of connection you will need a broadband router.