How to Ship a Package at the Post Office
Before you ship a package at the post office, make sure it's sealed shut and the address is clearly written on it. You should also include a return address in case the package can't be delivered. When you're ready to ship the package, bring it to the post office and have it weighed by a postal worker to figure out how much the postage will cost. Then, pay for the postage and apply it to the package in a visible location. Once you've applied the postage, simply leave the package with a postal worker, and you're done! If you want to be able to track the shipment, ask for a tracking number when you give them the package.
Use Retail Ground for the most affordable shipping option. Formerly known as Standard Post, Retail Ground is the cheapest way to ship a package via the USPS. But it is also the slowest, with a delivery rate between 2-8 business days. If time is not a huge concern for your shipment, then Retail Ground is a great option. Retail Ground can sometimes take up to 14 business days to deliver your package. The maximum weight for sending packages via Retail Ground is 70 pounds (32 kg). Use Priority Mail to pay a flat rate regardless of the weight of the package. Priority Mail has an expected delivery time of 1-3 days and includes free tracking. This shipping option offers many “flat rate” boxes, which means if the package fits inside of the standard box offered by the USPS, then the weight doesn't matter. This can take the hassle out of weighing the package and making sure you include enough postage. You can use Priority Mail to send packages weighing up to 70 pounds (32 kg). All of the boxes and envelopes for Priority Mail are free! You can request to have them shipped to your home or office, or you can pick up what you need from the post office. Use Express Mail for the fastest delivery time. The Priority Mail Express option is the most expensive shipping option, but it is also the fastest and has a money-back guarantee. It is the USPS version of next day delivery, taking 1-2 business days to arrive. It also offers flat rate boxes that allow you to ship anything that fits as long as the package weighs less than 70 pounds (32 kg). Express Mail also has an expedited service to have your package delivered by 3 p.m. the next day. Express Mail also provides insurance coverage for up to $100, a signature confirmation of delivery, and tracking information. Note that Priority Mail Express often has a separate pick-up and drop-off time in order to arrive at its destination on time. Contact your post office by phone or go online to confirm the drop-off time. Use First-Class Mail to ship envelopes that weigh less than 13 ounces (370 g). The First-Class Mail shipping service is an affordable way to send a lightweight package quickly. Packages are delivered within 1-3 business days, and the USPS offers insurance for loss or damage up to $5,000 for merchandise. You can also add additional services like delivery confirmation, which allows you to track your package as it travels to its destination. Use padded envelopes to send First-Class Mail for their light weight and durability. To send a lightweight package via First-Class Mail, the envelope must not exceed 15 inches (38 cm) by 12 inches (30 cm), or your package will be charged at the next higher price or mailing category. Your package must be at least ⁄ 4 inch (0.64 cm) thick. If your package doesn't fit the dimensions, the USPS may return it, or automatically upgrade the shipping and charge the customer. Send books, CDs, and other media using Media Mail. The USPS Media Mail service is a cost-effective way to send media like sound and video recordings on a disk, manuscripts, sheet music, printed educational charts, medical binders, and computer-readable media safely across the country. Video games and computer hard drives do not qualify for Media Mail prices. Media Mail has a maximum weight of 70 pounds (32 kg). Ask a postal worker if your items qualify as Media Mail before you package it up and ship it from the post office. Place your shipment into a box or envelope and seal it shut. Fit your item or items into the box or envelope, add cushioning materials (like bubble wrap, newspaper, or packing peanuts) if necessary, and seal the envelope or tape the box shut with packing tape so that it closes flat on all sides. Reinforce the flaps on the top and bottom with tape so that the box doesn't open in transit. For Retail Ground and First Class Mail, you can use any sturdy cardboard box. You don't have to use the USPS Priority Mail box. Use a box that will hold your shipment, but leaves a little bit of room for you to add any padding material. If your box has other stickers or logos other than the USPS logo for Priority Mail boxes, you can cross them out with a marker or cover them with your postage label. Make sure your box does not have anything loose hanging from it like twine, string, or tape because it can get caught in the sorting equipment. Address the package clearly. You can use label stickers or write the address directly onto the package. Be sure to put a return address and include the zip codes. Use ink that doesn't smear so the address remains legible as it travels to its destination. Use a permanent marker if you're writing the address directly on the package. Bring your package to the post office to measure and weigh it. Before you can ship your package, you have to pay for the correct postage, which means you need accurate size and weight measurements. A postal worker at the retail counter of your post office will weigh and measure the package to determine how much postage it requires. They will also be able to inspect the package to confirm that it has been prepared correctly. When the postal worker calculates the necessary postage, be sure to ask about the cost for confirmation numbers as they may cost extra depending on your shipping method. Apply the postage to the package. After your package has been weighed and measured, you can purchase the necessary postage to have it shipped. Apply the postage to the package in a clearly visible location. The postage label will include a barcode that will be scanned as it is processed during its journey to be delivered, so make sure the label is easy to find and scan. A postal worker can also give the cost to ship for multiple methods so you can compare and choose the best option for your shipping needs. The postal worker at the post office will often apply the postage to your package for you if you purchased it from them. Postage always goes in the top-right corner of an envelope, but this can vary for packages. If you printed your own postage on regular paper, use clear tape and cover the paper entirely so it doesn't get too wet to read or scan. Give your package to the postal worker at the retail desk. The postal worker behind the counter can confirm that the package has been properly prepared and the correct postage has been applied. They will then scan the package and process it for delivery. They can also provide you with a confirmation or receipt of the transaction. Get a tracking number if desired. Tracking information allows you to follow the package in transit. This is a great feature if you need to check the status of a package or need to verify that it was delivered. It may cost extra for tracking information on a package being sent via First-Class Mail or Retail Ground, but it can give you peace of mind knowing the status of your shipment. Tracking information comes free with Priority Mail, Priority Express, and First-Class Mail. You can also get a signature confirmation if you need to verify that the package was received by a person. 
Use Retail Ground for the most affordable shipping option. Use Priority Mail to pay a flat rate regardless of the weight of the package. Use Express Mail for the fastest delivery time. Use First-Class Mail to ship envelopes that weigh less than 13 ounces (370 g). Send books, CDs, and other media using Media Mail. Place your shipment into a box or envelope and seal it shut. Address the package clearly. Bring your package to the post office to measure and weigh it. Apply the postage to the package. Give your package to the postal worker at the retail desk. Get a tracking number if desired. 