The three major wireless companies in the US are AT&T (formerly Cingular), T-Mobile, and Sprint. AT&T is best known for its wide coverage, however you may not feel a big difference. The network coverage can be checked in their Websites.

There are variety of options for the plan to use. Basically, there are two options to go for, prepaid and monthly-billed (post-paid):

For each of the pay modes, there are variety of plans that you can decide based on your usage. Prepaids are great if you immediately require phone after your arrival. But for long-term monthly-billed plans are more popular.The most preferable plans for a student would be the lowest rate monthly-billed plans such as "450 minutes - nation" from AT&T (450 min/5000 min N&W/Free to other AT&T customers) or "myFaves 300" from T-Mobile (300 min/Free N&W/Free to other T-Mobile).

Where to buy: 

You can get the phone/plan from the operators' self stores, or from Radio Shack (there is one in Forbes Ave in the Pitt campus area). Another option is ordering online through companies such as wirefly.com or Amazon.com. Those companies offer you some cashback or better handsets free of charge, provided you do not cancel your contract within 6 month of purchase. That is a good deal, however They don't usually have good customer services if you have some problem with your purchase (faulty handset/incorrect charge).

Some remarks:

• You are charged for both giving or receiving a call/SMS (not fare!)
• The same charge applies for making a call to a different operator's subscriber
• You'll get some percent discount on your bill as a university affiliate (provide your ID when you are getting the plan) 

Other links:

• A complete/sophisticated guide to cell-phone plans at about.com