Although our natural tendency is to try to achieve symmetry, remember that wear is often unbalanced. Try to keep your damage random. You don't have to buy special tools, just imagine any number of accidents that could happen throughout the years. If you have time, you can let nature take its course while speeding up the process a bit. Sunlight and water damage and age wood over time. Apply ingredients that will help lighten or darken areas of the wood. Use wood bleach to lighten spots or the whole project. Or rub in a bit of oil to darken random spots.
Before or after you apply the final finish, you can use any number of items to artificially create age. Roughing up an item to simulate years of wear is simple. Create dents with a hammer, chains or any other hard item. Set a cold glass of water down to create rings. Use nails or screws to make holes. Put a piece of paper down and write on it to create the illusion of years of use. Throw your key ring down on the project several times. Sand worn parts of your project to an extremely fine finish and leave the rest a bit rough. Use a torch to heat or burn the wood a bit. Scratch the wood with pens, nails or a letter opener.
One of the easiest ways to distress furniture is to paint it, then sand areas you wish to show wear. This technique works even better if you paint one coat, then paint another coat in a contrasting color. If your finished piece is white, paint black or dark brown first, then white. Lightly sand the natural wear areas until the contrasting color shows through. If you have created artificial wear, you can highlight the areas by applying darker paint or stain and then wiping it off before you finish the project. The darker color will remain in any indentations and around holes. Other ways to make paint look old include antiquing or crackle mediums. Spill a jar of ink and allow it to soak in a bit before you apply paint or stain.