Go to your dollar/office supply store, and buy a packet of colored stickers; the type used as "price tags". They come in a variety of shapes and sizes - try to get the larger size.
If you are moving long distance using a professional mover, try to make itemized list of what is in the boxes. We lost 9 boxes on our last move and lost money from insurance because we could not tell them exactly what was in each box.
Here are some tips for labeling boxes when you are moving. Label items with a large, dark colored permanent marker.