Securing a passport is necessary if you're planning on leaving the country and it's best to apply early to ensure successful travel. And if you already have one but haven't touched it in ages take it out of its hiding place to check the expiration date.
You may renew your passport through the mail if you have it in your possession (aka, not lost), you were at least 16 years old when it was issued, the passport itself isn't more than 15 years old, and you still have the same name or can provide proof of a legal name change. Find out how to obtain a brand new passport when you read more.
The process for a new passport isn't as simple as renewing an old one because you have to appear in person to apply. The good news is there are thousands of locations in the US that will accept your application, and when you go make sure you have two passport pictures, proof of US citizenship, and a valid photo ID.
There are now two options for traveling abroad: the passport book and the passport card. The card is a cheaper alternative ($45 versus $100) but only valid for land and sea travel within North America and not for international air travel. A new passport book costs $100 (includes application and execution fees) and a renewal costs $75. Different acceptance facilities may have preferred methods of receiving payment; some may even require exact cash, so call ahead of time to find out exactly what is needed.
Find an acceptance facility near you, determine whether or not you need to appear in person to apply for a new passport, or print out a renewal form by visiting the government's Bureau of Consular Affairs website.