If you are staying in a Disney resort, you tell the castmember who is checking you out, that you want to have the package delivered to your resort. You will fill out a piece of paper that has your resort name on it. You will be given a carbon copy of the form and your receipt. Your package should be delivered to your resort within 24 hours. Obviously, you couldn't use this option if you were checking out the next day. The package pickup location in the resort is usually in the resort store.
You can also have your package delivered to Package Pickup. Package Pickup is situated close to the park entrance in each of the theme parks. Tell the castmember that you want the package sent to Package Pickup. You'll fill out a piece of paper and given a carbon copy and the receipt. You can not have a package delivered to package pickup if the park is closing in less then 3 hours. In other words, if the park is closing at 9:00 p.m., your deadline for having a package sent to package pickup is 6:00 p.m.
If you are staying offsite, you can still have your packages delivered to Package Pickup.
You can not send anything that is perishable to package pickup.
Hope I didn't make that sound too complicated because it really isn't.