You really need to set up only one thing, a Yahoo! ID. Doing that immediately gets you a number of services you can access through Yahoo! Mobile.

Along with doing that on a PC's browser, there are other services you can sign up for or customize. Consider getting a Flickr account. That involves a separate sign up. You can also add preferences and special options in Yahoo! News, Yahoo! Sports, Yahoo! Finance, Yahoo! Weather, and Yahoo! Movies. These are available to you just by having a Yahoo! ID.

Availability of some services depends on the device, carrier, and service plan you have. Consult your carrier.