Summarize the following:
A utility trailer should be customized to your specifications. You will need to decide on the length, the weight capacity, and whether or not it will be enclosed. For example:  If the utility trailer will be used for lumber or building materials, it may need stronger suspension and larger wheels. For ease of loading and unloading—especially lumber—you would probably not want it enclosed. You would also want to make it long enough to hold lumber and sheeting. For machinery and valuable tools, you would not only want it sturdy, but also enclosed and secure to prevent theft. The vehicle that you will use to pull the utility trailer will also help determine the dimensions. For example, a utility trailer to haul groceries behind a bicycle will necessarily be much smaller than a utility trailer for a Suburban, built to haul a table saw. You may choose to build a utility trailer from scratch or assemble a kit. Either way, the right tools and materials are essential. Search online websites for utility trailer kit plans or visit a home improvement store, or tractor supply dealer for ideas. In the planning stages, it's important to be aware of your construction and mechanical expertise and capabilities. Building a utility trailer from scratch will require welding skills, an aptitude for carpentry, and electrical knowledge to install taillights. It also helps if you're comfortable with heavy lifting.
Determine the type of trailer you'll need. Decide the method of construction. Confirm your level of ability.