Hi Stewart and welcome to GoY. If you are asking about the Japanese Acers these are propagated from softwood cuttings. I can do no better than refer you to the RHS website which has excellent info on how to take softwood cuttings, copy and paste the url below into your web browser

http://bit.ly/N9iKnv

The majority of acer palmatum varieties we buy are grafted on to root stock ,one of the reasons being it provides a better tree quicker than those from cuttings which i believe are not easy for us amatuers!.

I would agree Dgw but it is possible. Personally I wouldn't do so :-)

I have tried several times to take cuttings from Acers, but have been unsuccessful, sorry.