Assuming you live in the United States, you'll want to change your address with the U.S. Postal Service, but before you do, you'll have to decide whether to file a temporary or permanent change of address (COA).
A permanent COA is just that; it allows your mail to be forwarded to your new permanent address for a specified period of time. It covers first-class mail and periodicals, but generally doesn't forward standard mail, such as circulars and catalogs. With a permanent COA your new address is made available to companies who subscribe to the National Change of Address Service and provided to business mailers upon request.
If you plan on spending winter in a warmer spot or summer somewhere cool, a temporary COA might be for you. This service allows you to have first-class mail and periodicals forwarded piece by piece to a different address for your specified period of time, from 15 days to 6 months. If you just aren't ready to come home yet, you can extend the service up to 12 months.
Premium forwarding service is an alternative to the temporary COA. However, rather than the piece-by-piece forwarding, all of your mail, including standard and package service, is packaged in a single shipment and sent to you by priority mail each Wednesday. There is a one-time enrollment fee and a nominal weekly reshipment fee for this service.
Unlike the permanent COA, with the temporary options your address will not be provided to business mailers. That's one way to avoid junk mail.