Methods for seasoning wooden spoons?
I cannot imagine that sanding and buffing a wooden spoon would have any useful culinary applications, although I suppose it might feel smoother to the touch.

Generally when you season something wooden for food preparation, the purpose is to create a protective layer to avoid warping or impregnation.

If I really wanted to season a spoon, I would season it the same way as a wooden cutting board: Use a food-grade mineral oil and rub it in thoroughly with a cloth or paper towel, then repeat as necessary after it is dry.

Like hobodave, however, I have never done this nor heard of it being done.  The cost of a wooden spoon is probably less than the cost of the mineral oil you'd need to season one.  If your spoon starts to warp or take on strange odours, just buy a new one.

N.B. I can think of one exception, which is if the spoon takes on a fuzzy texture when you get it wet.  In that case, sanding it would be done in the context of raising the grain.  But once again, it's extremely rare that you'd need to do this with a cooking utensil - this is a far more common requirement for homemade (i.e. DIY) wood products.