I am going to the USA for 3 weeks. I would like to order some goods over the internet, to be delivered to me, while I am there. Specifically Florida, if that makes a difference.
How do I best proceed to do this?
I will be staying at hotels/motels.
In some countries, it's possible to have mail delivered to a larger post office, and collect it from there. The general term for this is Poste Restante (also used in English speaking countries like the UK), but in the USA is called General Delivery. Assuming the thing you order will be delivered by the USPS (and not a courier), by using a General Delivery address (details on wikipedia) you can have the mail arrive up to 30 days before you do.
If it might come by courier, or you won't be near the main post office for the area where you'll be, your best bet is to have it sent to a hotel you'll be staying at. (Not sure if a Motel will work though). Almost all hotels will be fine to have mail or packages delivered there for you. Many (especially bigger or nicer ones) will charge you a small fee for this, depending on the size of item.
Quite a few hotels will be willing to let you have mail or packages sent there in advance, ready for you to collect at checkin. (Bigger ones are normally fine with this, as are business focused ones, and some friendly small ones too). Can work quite well - you check in, get your room key, and get the parcel that was waiting for you! Bigger hotels normally charge for this, typically the same rate as for any received mail / packages (unless it was there for ages), small family run places that offer it seem not to charge.
If you do go down the hotel route, speak to / email with the hotel in advance. Firstly, you need to check they offer the service! Secondly, you need to find out what to put on the address. Some are happy with "Your Name, Hotel's Name, Hotel's Address". Others want "Your Name, Guest from XXX to YYY, Hotel Name + Address". Some need "Your Name, Guest Services / Mail Services / Something Else, Hotel Name, Hotel Address". Find out so you know what to use! You can also then check about if they can accept things in advance (and how far), and what fees (if any) they charge
Finally, assuming you're ordering online, have a quick chat with your credit card company in advance. Someone ordering something online for delivery to a Poste Restante or Hotel address in another country to where you are can make the fraud team nervous, so check what (if anything) you need to do to let the transaction go through.
I usually ask at the front desk of the hotel. Tell them that you're expecting a delivery and politely ask them to hold it for you.
Most reputable hotels that I've stayed in are happy to hold small good for you. Obviously, don't get a refrigerator delivered :-)
I've never tried this in a motel. You could put your room number on the delivery instructions - but that means you have to stay in all day.
Depending on where you're traveling, a certain largest online retailer of the world offers a Locker Service which, when available, is the ideal solution here. Just order what you want from Amazon, select Amazon Locker as the delivery method, and when you get the delivery notification, just pick it up from the locker, (most of which are accessible 24/7, and located in convenience stores.).
Alternately, I travel for work, and need to have items shipped to me at hotels on a weekly basis - no hotel has ever had an issue receiving my package for me, and doing so is perfectly normal for them. Most will have procedures in place and shouldn't charge you or hassle you over it at all.
Most of the courier services (UPS, FedEx) will hold packages for pick up at their office, similar to the General Delivery service from the post office mentioned earlier. Depending on where you are visiting, some cities multiple branches in town, some have only one. You can specify which branch if you are sending them to e bigger town. But small rural towns would not have an office, you have to have the package sent to your hotel or use the General Delivery method of USPS.