You don't need a spell, just go into the forest and pick up any stick that is of good length, width and not rotted. After using it for a while your wand will become charged with your energy and it will greatly increase it's power. :)
I like to take the stick and carve it, or just carve a symbol into it. If you want out to be a special purpose wand, you can connect it to an element by buryI ing it for Earth, burning it for Fire (which adds destructive properties), soaking it in rose or sweet water, or ....I don't know how you'd connect it with Air. >_< Then I focus on one property that I need when I'm casting, so say I need to heal someone, if focus on health and light, and then I make a cut on the end of the wand where I hold it. I do this for three properties. Sometimes I anoint it with a little of the connected oil to add more to it, and then I charge it with the appropriate energy.
This is just my personal ritual, but I'm sure its good for anyone! ^_^