It is really not that easy to root Japanese Maple - Most if not all are grafted and that takes time, the "right" conditions, sucess and failure, on and on - It is not that easy.
Best bet is to go to a nursery and purchase.

Good advice from plantman.

Perennialfan, there are only a few cultivars that are considered 'easy' to root. There is controversy about the merits of own roots vs grafted plants but in general rooted cuttings from cultivars are desirable and many are not at all easy to acquire. Essence of the Tree in Cali had a nice selection of rooted cuttings in their 09 catalog.

Here is a link that might be useful: Essence of the Tree