Shields can have some added flair with banners, adding damage absorption and an excuse to show off designs. This is easily done with some wool and any color will do.
Crafting The Banner
Using six blocks of wool and one stick, a banner can be crafted using the Crafting Table. The bottom center should have the stick while the center and top grids should have all six blocks of wool for the recipe.
After crafting a shield with wood planks and iron, it can be combined with a banner in the crafting menu. This can be seen automatically in the crafting menu, but the recipe is having the shield in the center tile with the banner to the left or right of it. Wool can be obtained from sheep and different colored wool can be acquired by using dye on the sheep before killing or shearing them.
Related: How to make Shears in Minecraft
Customizing Your Banner
Using a Loom, made with two wooden planks and two pieces of string, the banner can be further customized with different designs. This is done by placing the banner in the Loom menu and adding any color of dye to add preset designs. Each piece has its own name so following guides for a specific design is simple by using the names of those decorations. Once one design is selected and printed to a banner, another can be added in for different colors or making letters, faces, and even the Mojang logo.
Preserving Your Shield
Using enchantments for the shield such as Unbreaking and Mending will preserve it for as long as possible. When the durability starts to get low, if players would like to keep their enchantments as well as their banner, they will have to remove the banner. The banner can be remade easily, but an enchanted shield may be expensive to replace. Simply craft a new shield and make the banner again and combine the two using the Anvil with the new shield on the left.
To remove the banner from a shield, the same method can be used but with a blank banner to clear the design. Unless it's enchanted, however, it may not be worth the XP dump and might be better to just craft a new shield and banner from scratch.
For more information regarding banner designs, check out How to Make All Banner Patterns in Minecraft on Pro Game Guides.