Weight is an important consideration. If your yard jockey is made out of concrete or cast iron, the weight can be a factor. Many household shipping companies will not ship past a certain weight. For example United Parcel Service will not ship over 150 pounds by regular household trucks, but require the services of UPS Freight. Obtain a household scale and weigh your jockey. If the weight is beyond the limits of some carriers, then you will have to crate it and secure the crate to a pallet. Freight carriers will then be able to ship it.
Another consideration is damage. If your yard jockey is made out of concrete, it will not take stresses well. You will have to protect it by bubble wrapping, and enclosing it snugly in a crate so it doesn't rattle around. Yard jockeys made out of plastic composites are durable and lightweight, but still should be wrapped up in bubble wrap to prevent damage. A solid crate made out of thin plywood is suitable to prevent damage to either one.
Some carriers will not ship a crate past certain size dimensions. UPS, for example, has a limitation of 108 inches in length. They are able to ship larger packages through their freight division, but freight charges apply. Other carriers have different policies, so it's best to shop around for a carrier that can offer the cheapest rate.
Loss and damage insurance should be on the checklist as well. If your yard jockey is an antique, then it is best to have it professionally appraised, to set an amount on the loss and damage policy. All carriers offer insurance. Purchase the level of coverage of the appraisal, and make sure the policy specifies what criteria apply for reimbursement in case of carrier damage.