Summarize:

You can do this either by email or phone, and tell them specifically what you're looking for in order to find out of they can supply a container that meets your needs. If you have found several potential dealers, you should consider contacting all of them to see who will give you the best deal. If there is one who will allow you to see the container, it might be wise to go with them simply because you will get a chance to inspect the quality. Ask the seller to give you a chance to examine the container. However, be aware that this may not always be possible as some sellers may have thousands upon thousands of containers in the depot. If the seller will allow you to, examine the container you will be purchasing carefully.  If you need the container to be wind and water tight, go inside the container and shut the door. It will be dark, so you should look for any places where light shines through. If you find a place, this means that it may not be able to protect you or your things from the elements.  Make sure the doors close properly, and that there are no huge dents in the container.  Containers tend to rust a bit, especially if they are not “new”, but you should look for areas where the container is rusted through. If you need to have your container shipped to you, it is recommended that you do your best to request delivery via a tilt bed roll off truck.  Remember though, that unloading, especially if you are having the delivery person place it in a specific way, will cost extra. The price may be included, but it may not be, and it can vary greatly. Make sure you negotiate this cost with the seller. Containers weigh, depending on size, approximately 5,000 pounds (2,268 kilos), so you definitely can’t manage it alone!  If you want to have your shipping container placed in an area that doesn't have much cleared space, then you may have to hire someone with a crane to lift the container into the desired position. In countries such as the US, most dealers have many more containers than they need, so it is in their interest for you to purchase one. This gives you the power to negotiate the price with the dealer! If they won’t budge on the price, try asking for free delivery. Although you should negotiate the price, avoid taking advantage of the seller. He or she will know that you are, as they know the going rate. They will be less likely to work with you if they feel you are trying to take unfair advantage over them.
Contact the seller. Ask to see the container. Inspect the container. Negotiate shipping. Negotiate an offer.