First step is to pick a mail forwarding service. I recommend implementing that service weeks or months in advance. Notify all your banks, financial institutions, and everyone else you can think of. Be sure to file the change of address using the IRS form 8822. Do not rely on the US postal service to forward your mail to your new address. That is a haphazard unreliable manual process that often fails.
The second step is to try to eliminate all snail mail. Set everything up electronically with financial institutions. You should be able to eliminate almost all mail. To actually receive your mail, you will need to remain in the same location for several days. Check with the local post office to be sure they handle general delivery and then arrange a shipment from your mail forwarding service. For the first year, I made arrangements for forwarding every month or so. Later on I often waited several months for forwarding.