You have a plot of land you wish to enclose. First you need to ask yourself for what purpose. If to retain horses or livestock, you might need to consider an electrified fence. For domestic pets such as medium or large dogs, a chain link fence might be your best bet. Perhaps you simply wish to liven up your yard or establish/highlight property lines for your neighbors.
Regardless of the original purpose, always buy a fence at least one level stronger than you would image necessary. A sturdy fence will never be a poor investment, cheaping out always will be. Fences can last from 5-100 years depending on the materials used, the extent to which they are installed, and of course, the environment they protect. The best material to use for a lasting fence that combines functionality and aesthetics in my opinion is cedar.
Over the years, split rail cedar fences turn a beautiful soft silver while its structural integrity holds strong. If a rail is broken by a charging bull or other intense force, simply replace the damaged rails rather than having to re-due any posts or even worse, an entire section as you might with other fences.
If you have a tighter budget, consider vinyl fencing. Typically three rails high, vinyl fencing is a great solution for retaining large animals only (as a dog or cat can easily run under). Vinyl fencing gives a little when leaned on as opposed to wood or metal. One neat feature about vinyl fencing is the customization abilities. Being a simple assemble with no specific holes or grooves, vinyl fencing can be cut down to any desirable length making a curved edge possible as well as a lower one if you cut down the posts. Vinyl fencing however is best installed with cement poured in around a foot and a half deep. This is quite an undertaking and if indenting to install the fence yourself, the best way to dig is with a Little Beaver Earth Auger which should not be hard to rent.
Plastic Fence Installation: