Be familiar with the laws in the states you drive in. You should look at your cargo covers in the mirrors from time to time while driving. A flapping cover can tear loose, uncovering the cargo, and possibly blocking your view or someone else's. You cannot inspect sealed loads, but you should check that you don't exceed gross weight and axle weight limits. Containerized loads generally are used when freight is carried part way by rail or ship.
Some containers have their own tiedown devices or locks that attach directly to a special frame.
Others have to be loaded onto flat bed trailers. They are secured with tiedowns just like any other large cargo. Hauling liquids in tanks requires special skills because of high center of gravity and liquid movement. High center of gravity means that much of the load's weight is carried high up off the road. This makes the vehicle top-heavy and easy to roll over.