This is my first Instructable, so if you want to give some constructive criticism, your welcome, but keep in mind that I am a younger person.
Step 1: Dowel Rods
I'm not going to tell you a specific length (because all wizards have different tastes), but if you just want to go by the standard, buying a foot long dowel rod at a craft store is the way to go. Otherwise, you can buy the full length dowel rod at cut it to your size of preference. You want to buy one of the thinner ones, but again, it's up to you and your desire.
Step 2: Sand the "Tip" of Your Wand
Use a nail filer (or someting of that nature) to sand one end of your dowel rod to a point, or, you can round it off like the picture shown.
Step 3: Color the Handle
Hold the dowel rod in the same way that you would hold a wand. Make a mark where your hand ends on the rod and color downward the color of your choice. You can use paint, or the ever-so-trusty Sharpie marker.
Step 4: Color Remaining Area
Now, there should be a large area of uncolored dowel. You can keep it simple and color it with brown or black. You can even leave it the off-white color that it is. Or, if you're a more vibrant personality, you can use any color in the rainbow! Even two or more!
Step 5: Bonus
You can spice up your new wand with a strip of thin metal like the binding of a composition notebook. Wrap it around the handle in any twisty form you want!